why is my audio suddenly out of sync after importing a synced video file from riverside.fm?

hello! please help! I keep running into this same problem. whenever i imported a synced video file into final cut pro fro riverside FM the audio shifts completely. to explain in more detail. i have an guest who joins a podcast after ten minutes. so his synced audio file when i export it has 10 minutes of black space so it lines up with the main video in editing. totally normal. but once i import this video clip into final cut pro, somehow the audio jumps top the begginer of the video. so its a black screen with audio over it. audio that sint supposed to start till the 10 minute mark! and the wave forms dont change! even they are still at the 10 minute mark! but somehow thaudio plays out of sync from the beginning of the video