Unfortunately that didn’t work. I got the same error at the same 99.4% completion when demuxing as I did when muxing. I did notice that TSmuxer had some additional info in a little window near the bottom. It said something about the streams possiby being out of sync or something like that (I really should’ve screenshotted that…)

Anyway, I’m wondering if somehow the MKV was corrupted or incomplete. I decided to just scrap it and start over, so I deleted the MKV and am currently re-downloading it. hope it works this time! What’s odd, though, is that VLC had no problem playing the MKV. But I didn’t actually watch the whole film, just spot checked it. Perhaps VLC would’ve locked up once it reached the broken part. I’ve seen VLC do that before, where you have a failed download that will play fine until it reaches the broken bit.