Audio popping or silent inconsistently in Final Cut Pro with Riverside FM files
I'm editing a podcast interview recorded in Riverside FM for the first time. I have two MPEG 4 files, one for each person's side of the interview.
When I playback or export as MP4, there are random places of loud popping where clips are joined, or entire clips that are completely silent, and it's different every time I playback or export a new MP4.
Most of the clips have audio, but a random clip might have audio one time, but not the next, while a different one is silent the next time. Same with popping.
I added crossfades to all clips, but it hasn't made a difference.
Finally, the entire project has been sluggish to work with in FCP. Lots of delay and the spinning wheel as I edited.
I played back a previous project in FCP to verify if it was just "this" project, or something else going on, and that one has no issues with audio or sluggish behavior.
FCP Version 10.6.2
IOS Venture 13.3.1
Thanks for any suggestions.