PP2020 Export to Media Encoder not muxing mp4

I've got an hour and 58 minute mp4 recording from MS Teams that I've edited 16 minutes out of in various places. I export to Media Encoder, select my settings (also a low res mp4, manually adjusting the bitrate down to 1mbps to match the source) and let it fly. 15 minutes later, it spits out an mp4 and m4v but never muxes the two together. The two are also no where near the size they should be (just over 115MB combined vs the 700+MB) I've tried numerous times, same result. Not sure what else I can do. Anyone have any ideas?