This is the second time it happens and it happened with two completely different series so I think other Infuse users might have had the same problem.
I've downloaded a TV series in mp4 format and some episodes don't work. Most do, but some don't. When I open the broken ones with Infuse I can see the playback slider jumping on random timings (like 1:42, 5:28, 20:10) and then CTD. These files work perfectly fine on PC and, more importantly, on other iOS players (I checked with VLC and OPlayer) so it's definitely an Infuse compatibility issue with some non-standard encoding.
If you devs are interested I can run any check you want on these files, but I can also privately link you the torrent from which download them if you want. Thanks for reading!