some MP4 files will not play in VideoBox

[markflickr]

They play absolutely fine in media player or VLC and i can't see any difference between the ones that play fine in VB and the ones that don't.
what specifics should i look out for? I could do with some pointers.
I use the system as a music video player.
Video files are mostly downloaded from Youtube
K-Lite is already installed (latest version)
Graphics are Radeon RX570 and drivers fully up to date.
system is W11 although i had the same problem on W10

[Steve]

Hi, if you want to send me a couple of smaller files I will take a look ?, 1 that plays and 1 that doesn't in a zip.

[markflickr]

would you believe i fixed it.
i re-encoded the video files through VLC to H264 + MP3 then told it to leave the audio unchanged and that fixed it.
I'll come back to you if i get any more problems.