Pretty much the exact thing that's detailed in this thread: https://firecore.com/forum/topic/22576 . A horrible continuous "Twinging" tone after fast forwarding or rewinding seemingly random movies & shows. It doesn't happen every time and is pretty intermittent.
I have 2 completely different receiver and ATV setups and they both exhibit the same issue. So it's not a bug on my end.
Zero issues playing the same content with the Plex or MrMC apps.