Only the last cell associated with a media adapter should clear its views.

// FREEBIE

Signal/src/Models/TSMessageAdapaters/OWSMessageMediaAdapter.h

@@ -8,7 +8,11 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)setCellVisible:(BOOL)isVisible;
 
-- (void)clearCachedMediaViews;
+// Cells will request that this adapter clear its cached media views,
+// but the adapter should only honor requests from the last cell to
+// use its views.
+- (void)setLastCell:(nullable id)cell;
+- (void)clearCachedMediaViewsIfLastCell:(id)cell;
 
 @end
 

Signal/src/Models/TSMessageAdapaters/TSAnimatedAdapter.m

@@ -21,6 +21,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic) TSAttachmentStream *attachment;
 @property (nonatomic, nullable) AttachmentUploadView *attachmentUploadView;
 @property (nonatomic) BOOL incoming;
+@property (nonatomic, nullable, weak) id lastCell;
 
 @end
 
@@ -79,6 +80,15 @@ NS_ASSUME_NONNULL_BEGIN
     }
 }
 
+- (void)clearCachedMediaViewsIfLastCell:(id)cell
+{
+    OWSAssert(cell);
+
+    if (cell == self.lastCell) {
+        [self clearCachedMediaViews];
+    }
+}
+
 #pragma mark - JSQMessageMediaData protocol
 
 - (UIView *)mediaView {

Signal/src/Models/TSMessageAdapaters/TSGenericAttachmentAdapter.m

@@ -21,6 +21,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic) TSAttachmentStream *attachment;
 @property (nonatomic, nullable) AttachmentUploadView *attachmentUploadView;
 @property (nonatomic) BOOL incoming;
+@property (nonatomic, nullable, weak) id lastCell;
 
 @end
 
@@ -210,6 +211,15 @@ NS_ASSUME_NONNULL_BEGIN
     // Ignore.
 }
 
+- (void)clearCachedMediaViewsIfLastCell:(id)cell
+{
+    OWSAssert(cell);
+
+    if (cell == self.lastCell) {
+        [self clearCachedMediaViews];
+    }
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

Signal/src/Models/TSMessageAdapaters/TSPhotoAdapter.m

@@ -16,6 +16,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, nullable) UIImageView *cachedImageView;
 @property (nonatomic, nullable) AttachmentUploadView *attachmentUploadView;
 @property (nonatomic) BOOL incoming;
+@property (nonatomic, nullable, weak) id lastCell;
 
 @end
 
@@ -145,6 +146,15 @@ NS_ASSUME_NONNULL_BEGIN
     // Ignore.
 }
 
+- (void)clearCachedMediaViewsIfLastCell:(id)cell
+{
+    OWSAssert(cell);
+
+    if (cell == self.lastCell) {
+        [self clearCachedMediaViews];
+    }
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

Signal/src/Models/TSMessageAdapaters/TSVideoAttachmentAdapter.m

@@ -30,6 +30,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, nullable) AttachmentUploadView *attachmentUploadView;
 @property (nonatomic) BOOL isAudioPlaying;
 @property (nonatomic) BOOL isPaused;
+@property (nonatomic, nullable, weak) id lastCell;
 
 @end
 
@@ -294,6 +295,15 @@ NS_ASSUME_NONNULL_BEGIN
     // Ignore.
 }
 
+- (void)clearCachedMediaViewsIfLastCell:(id)cell
+{
+    OWSAssert(cell);
+
+    if (cell == self.lastCell) {
+        [self clearCachedMediaViews];
+    }
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

Signal/src/views/OWSIncomingMessageCollectionViewCell.m

@@ -30,10 +30,22 @@ NS_ASSUME_NONNULL_BEGIN
     self.expirationTimerViewWidthConstraint.constant = 0.0f;
 
     [self.mediaAdapter setCellVisible:NO];
-    [self.mediaAdapter clearCachedMediaViews];
+
+    // Clear this adapter's views IFF this was the last cell to use this adapter.
+    [self.mediaAdapter clearCachedMediaViewsIfLastCell:self];
+    [_mediaAdapter setLastCell:nil];
+
     self.mediaAdapter = nil;
 }
 
+- (void)setMediaAdapter:(nullable id<OWSMessageMediaAdapter>)mediaAdapter
+{
+    _mediaAdapter = mediaAdapter;
+
+    // Mark this as the last cell to use this adapter.
+    [_mediaAdapter setLastCell:self];
+}
+
 // pragma mark - OWSMessageCollectionViewCell
 
 - (void)setCellVisible:(BOOL)isVisible

Signal/src/views/OWSOutgoingMessageCollectionViewCell.m

@@ -31,10 +31,22 @@ NS_ASSUME_NONNULL_BEGIN
     self.expirationTimerViewWidthConstraint.constant = 0.0f;
 
     [self.mediaAdapter setCellVisible:NO];
-    [self.mediaAdapter clearCachedMediaViews];
+
+    // Clear this adapter's views IFF this was the last cell to use this adapter.
+    [self.mediaAdapter clearCachedMediaViewsIfLastCell:self];
+    [_mediaAdapter setLastCell:nil];
+
     self.mediaAdapter = nil;
 }
 
+- (void)setMediaAdapter:(nullable id<OWSMessageMediaAdapter>)mediaAdapter
+{
+    _mediaAdapter = mediaAdapter;
+
+    // Mark this as the last cell to use this adapter.
+    [_mediaAdapter setLastCell:self];
+}
+
 // pragma mark - OWSMessageCollectionViewCell
 
 - (void)setCellVisible:(BOOL)isVisible