Broken with new 4.5 cache implementation; the loop for building
image sequence proxies was not flushing the intra-frame cache
between frame changes. This affects image proxies since they go
through the whole VSE render stack; does not affect video proxies
since they just manually decode the file frames.
Pull Request: https://projects.blender.org/blender/blender/pulls/144269
1cf265988b