Steps to reproduce:
1. Open "StillSpace.zip"

0x000000014113F870 (Unity) VideoClipPlayback::IsPlaying
0x000000014113FAD3 (Unity) VideoClipPlayback::IsPlaying
0x00000001411408E8 (Unity) video_YUV420_convert::DecodeYUVFrame
0x000000014115EF02 (Unity) VP8VideoMedia::GetNextVideoFrame
0x000000014150AC7B (Unity) VideoClipImporter::ResetPreviewTexture

Note: Rebuilding the library opens the project. Also crashes when applying transcode settings for ForestFootage.m4v (not always), messes up the preview picture (see GIF attached).

Actual: When importing the project it crashes on ForestFootage.m4v file and it crashes when applying the transcode settings.
Expected: Project should not crash while importing or applying transcode settings.

Reproduced on: 5.6.0b1,
Did not reproduce on: 5.5.0p2, 5.4.3p4 (did not load file correctly), 5.3.7p2