Same boring issue. I just found making "Show live issues" unchecked will avoid this typing issue for now (this checkbox is located at "General" tab of Xcode preferences).

Meet same issues, but on Simulator (Xcode 12.4 (12D4e)) only. After some research, I found this crash is lead by AVVideoCompositionCoreAnimationTool's +videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:inLayer: And I fixed it by replacing it w/ one below (but need to handle instruction.layerInstructions in this way): +videoCompositionCoreAnimationToolWithAdditionalLayer:asTrackID: Below is a sample Objective-C code works on both real device & simulator: ... // Prepare watermark layer CALayer *watermarkLayer = ...; CMPersistentTrackID watermarkLayerTrackID = [asset unusedTrackID]; // !!! NOTE#01: Use as additional layer here instead of animation layer. videoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithAdditionalLayer:watermarkLayer asTrackID:watermarkLayerTrackID]; // Create video composition instruction AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction]; instruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration); // - Watermark layer instruction // !!! NOTE#02: Make this instruction track watermark layer by the `trackID`. AVMutableVideoCompositionLayerInstruction *watermarkLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstruction]; watermarkLayerInstruction.trackID = watermarkLayerTrackID; // - Video track layer instruction AVAssetTrack *videoTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject; AVMutableVideoCompositionLayerInstruction *videoLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack]; // Watermark layer above video layer here. instruction.layerInstructions = @[ watermarkLayerInstruction, videoLayerInstruction, ]; videoComposition.instructions = @[instruction]; // Export the video w/ watermark. AVAssetExportSession *exportSession = ...; ... exportSession.videoComposition = videoComposition; ... And btw, if you just need to add an image as watermark, another solution by using AVVideoComposition's -videoCompositionWithAsset:applyingCIFiltersWithHandler: also works well on both real device & simulator, but I tested it and found it's slower. Seems this way is more suitable for video blender/filter.