"Invalid webm uploaded." On certain webms

[anoniniarz]

similiar to #265, but I have set file size correctly, and it does not matter.
Example "invalid" webm: https://files.catbox.moe/bstkqs.webm
Example "valid" (can be posted) webm: https://files.catbox.moe/uhnxk6.webm (9MB so size does not matter)

Tried using both local binaries of ffmpeg and ffprobe and the $PATH ones, does not matter.

[chanadmins]

first webm works on my vichan instance so probably something wrong with your configuration

[Zankaria]

first webm works on my vichan instance so probably something wrong with your configuration

What's your ffmpeg version? Neither file gives me errors

$ ffmpeg -version
ffmpeg version 4.2.7-0ubuntu0.1 Copyright (c) 2000-2022 the FFmpeg developers