As for the HEVC file - RARBG files in that time period are toast. <----In case that is one.
If you have the original - remux it with MKVToolNix V45 or better.
(that writes the missing ctts atom - and fixes the file)
If you don’t have the original - re-acquire it - then fix it.
Problem identified and cure discovered here:
IF that isn’t one of the aforementioned files - apologies - and good luck on the AVC file. The problem files are all HEVC from that source.
