Sounds cut off when exported

My piece plays fine on my computer with the MuseScore file open. So I don't think there's a soundcard issue. However, when I go to export as an mp3 or wav, the results don't play properly - various notes are very clipped, or are missed entirely.
The sounds I am using are free orchestral sounds from MuseHub. I can't narrow it down to one part or one bar. I've not had this issue before but I can see online that others have.
I've tried reinstalling, tweaking panning, tempo, downloading separate parts, but no success. I've also tried another computer for the export and the playback. The only way atm that I can get a recording is to record in the room from my computer speaker, which isn't ideal. Any suggestions?