I'm reluctant to provide specific recommendations, so I'll suggest some approaches to solving the problem:
a search for "MPEG4 validation" or "ISOBMFF validation" will probably get you to something like MP4Box, which has an online version - https://gpac.github.io/mp4box.js/test/filereader.html (and you can self-host), command line tools like https://github.com/amarghosh/mp4viewer and similar commercial options.
you could also use https://github.com/MPEGGroup/isobmff or similar software to build something yourself.