diff --git a/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.h b/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.h
index b561007fde..db8863aabd 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.h
+++ b/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.h
@@ -126,7 +126,7 @@ NS_DESIGNATED_INITIALIZER NS_SWIFT_NAME(init(grdbId:uniqueId:receivedAtTimestamp
                               wasIdentityVerified:(BOOL)wasIdentityVerified;
 
 + (instancetype)failedDecryptionForEnvelope:(SSKProtoEnvelope *)envelope
-                                    groupId:(nullable NSData *)groupId
+                           untrustedGroupId:(nullable NSData *)untrustedGroupId
                             withTransaction:(SDSAnyWriteTransaction *)transaction;
 
 + (instancetype)failedDecryptionForSender:(nullable SignalServiceAddress *)sender
diff --git a/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.m b/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.m
index 1bf73eee71..162990675b 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.m
+++ b/SignalServiceKit/src/Messages/Interactions/TSErrorMessage.m
@@ -314,7 +314,7 @@ NSUInteger TSErrorMessageSchemaVersion = 2;
 }
 
 + (instancetype)failedDecryptionForEnvelope:(SSKProtoEnvelope *)envelope
-                                    groupId:(nullable NSData *)groupId
+                           untrustedGroupId:(nullable NSData *)untrustedGroupId
                             withTransaction:(SDSAnyWriteTransaction *)transaction
 {
     SignalServiceAddress *sender = [[SignalServiceAddress alloc] initWithUuidString:envelope.sourceUuid];
@@ -323,9 +323,16 @@ NSUInteger TSErrorMessageSchemaVersion = 2;
         return nil;
     }
 
-    TSThread *thread;
-    if (groupId.length > 0) {
-        thread = [TSGroupThread fetchWithGroupId:groupId transaction:transaction];
+    TSThread *_Nullable thread = nil;
+    if (untrustedGroupId.length > 0) {
+        [TSGroupThread ensureGroupIdMappingForGroupId:untrustedGroupId transaction:writeTx];
+        TSGroupThread *_Nullable groupThread = [TSGroupThread fetchWithGroupId:untrustedGroupId
+                                                                   transaction:transaction];
+        // If we aren't sure that the sender is a member of the reported groupId, we should fall back
+        // to inserting the placeholder in the contact thread.
+        if ([groupThread.groupMembership isFullMember:sender]) {
+            thread = groupThread;
+        }
         OWSAssertDebug(thread);
     }
     if (!thread) {
diff --git a/SignalServiceKit/src/Messages/OWSMessageDecrypter.swift b/SignalServiceKit/src/Messages/OWSMessageDecrypter.swift
index e3df401f2b..8104270e7b 100644
--- a/SignalServiceKit/src/Messages/OWSMessageDecrypter.swift
+++ b/SignalServiceKit/src/Messages/OWSMessageDecrypter.swift
@@ -285,7 +285,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
     private func processError(
         _ error: Error,
         envelope: SSKProtoEnvelope,
-        groupId: Data?,
+        untrustedGroupId: Data?,
         cipherType: CiphertextMessage.MessageType,
         contentHint: SealedSenderContentHint,
         transaction: SDSAnyWriteTransaction
@@ -346,13 +346,13 @@ public class OWSMessageDecrypter: OWSMessageHandler {
                     // If default, insert an error message right away
                     errorMessage = TSErrorMessage.failedDecryption(
                         for: envelope,
-                        groupId: groupId,
+                        untrustedGroupId: untrustedGroupId,
                         with: transaction)
                 case .resendable:
                     // If resendable, insert a placeholder
                     errorMessage = OWSRecoverableDecryptionPlaceholder(
                         failedEnvelope: envelope,
-                        groupId: groupId,
+                        untrustedGroupId: untrustedGroupId,
                         transaction: transaction)
                 case .implicit:
                     errorMessage = nil
@@ -587,7 +587,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
             let wrappedError = processError(
                 error,
                 envelope: envelope,
-                groupId: nil,
+                untrustedGroupId: nil,
                 cipherType: cipherType,
                 contentHint: .default,
                 transaction: transaction
@@ -691,7 +691,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
             return .failure(handleUnidentifiedSenderDecryptionError(
                 error: outerError.underlyingError,
                 envelope: envelope.buildIdentifiedCopy(using: outerError),
-                groupId: outerError.groupId,
+                untrustedGroupId: outerError.groupId,
                 cipherType: outerError.cipherType,
                 contentHint: SealedSenderContentHint(outerError.contentHint),
                 transaction: transaction)
@@ -700,7 +700,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
             return .failure(handleUnidentifiedSenderDecryptionError(
                 error: error,
                 envelope: envelope,
-                groupId: nil,
+                untrustedGroupId: nil,
                 cipherType: .plaintext,
                 contentHint: .default,
                 transaction: transaction)
@@ -760,7 +760,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
     func handleUnidentifiedSenderDecryptionError(
         error: Error,
         envelope: SSKProtoEnvelope,
-        groupId: Data?,
+        untrustedGroupId: Data?,
         cipherType: CiphertextMessage.MessageType,
         contentHint: SealedSenderContentHint,
         transaction: SDSAnyWriteTransaction
@@ -771,7 +771,7 @@ public class OWSMessageDecrypter: OWSMessageHandler {
         } else if isSignalClientError(error) {
             return processError(error,
                                 envelope: envelope,
-                                groupId: groupId,
+                                untrustedGroupId: untrustedGroupId,
                                 cipherType: cipherType,
                                 contentHint: contentHint,
                                 transaction: transaction)
diff --git a/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.h b/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.h
index d08b1614c1..aaea6374a6 100644
--- a/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.h
+++ b/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.h
@@ -10,7 +10,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initErrorMessageWithBuilder:(TSErrorMessageBuilder *)errorMessageBuilder NS_UNAVAILABLE;
 - (nullable instancetype)initWithFailedEnvelope:(SSKProtoEnvelope *)envelope
-                                        groupId:(nullable NSData *)groupId
+                               untrustedGroupId:(nullable NSData *)untrustedGroupId
                                     transaction:(SDSAnyWriteTransaction *)writeTx NS_DESIGNATED_INITIALIZER;
 - (nullable instancetype)initWithCoder:(NSCoder *)coder NS_DESIGNATED_INITIALIZER;
 
diff --git a/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.m b/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.m
index 4995f7860f..0e4f52023a 100644
--- a/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.m
+++ b/SignalServiceKit/src/Messages/OWSRecoverableDecryptionPlaceholder.m
@@ -11,7 +11,7 @@ NS_ASSUME_NONNULL_BEGIN
 @implementation OWSRecoverableDecryptionPlaceholder
 
 - (nullable instancetype)initWithFailedEnvelope:(SSKProtoEnvelope *)envelope
-                                        groupId:(nullable NSData *)groupId
+                               untrustedGroupId:(nullable NSData *)untrustedGroupId
                                     transaction:(SDSAnyWriteTransaction *)writeTx
 {
     SignalServiceAddress *sender = [[SignalServiceAddress alloc] initWithUuidString:envelope.sourceUuid];
@@ -21,8 +21,14 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     TSThread *thread;
-    if (groupId.length > 0) {
-        thread = [TSGroupThread fetchWithGroupId:groupId transaction:writeTx];
+    if (untrustedGroupId.length > 0) {
+        [TSGroupThread ensureGroupIdMappingForGroupId:untrustedGroupId transaction:writeTx];
+        TSGroupThread *_Nullable groupThread = [TSGroupThread fetchWithGroupId:untrustedGroupId transaction:writeTx];
+        // If we aren't sure that the sender is a member of the reported groupId, we should fall back
+        // to inserting the placeholder in the contact thread.
+        if ([groupThread.groupMembership isFullMember:sender]) {
+            thread = groupThread;
+        }
         OWSAssertDebug(thread);
     }
     if (!thread) {
diff --git a/SignalServiceKit/src/Storage/AxolotlStore/SenderKeyStore.swift b/SignalServiceKit/src/Storage/AxolotlStore/SenderKeyStore.swift
index 80c9052500..c8aff520d8 100644
--- a/SignalServiceKit/src/Storage/AxolotlStore/SenderKeyStore.swift
+++ b/SignalServiceKit/src/Storage/AxolotlStore/SenderKeyStore.swift
@@ -103,7 +103,11 @@ public class SenderKeyStore: NSObject {
             let distributionId = distributionIdForSendingToThreadId(thread.uniqueId, writeTx: writeTx)
             guard let keyMetadata = getKeyMetadata(for: distributionId, readTx: writeTx) else { return }
 
-            if !keyMetadata.isValid {
+            let currentKeyRecipients = Set(keyMetadata.keyRecipients.keys)
+            let currentGroupMembership = thread.groupMembership.fullMembers
+            let didSomeoneLeaveTheGroup = currentKeyRecipients.subtracting(currentGroupMembership).count > 0
+
+            if !keyMetadata.isValid || didSomeoneLeaveTheGroup {
                 setMetadata(nil, for: distributionId, writeTx: writeTx)
             }
         }