Alright, thanks! I'll do so in the coming days!

Hey, sorry that it took me so long... I kinda lost track of it, so thanks for the reminder. I created a feedback (FB9243197). I hope it helps! Also, the error message the writer gives me on failing is "Cannot Encode".

Yeah sure, sorry, could have thought of that myself. Error Domain=AVFoundationErrorDomain Code=-11840 "Cannot Encode" UserInfo={NSLocalizedDescription=Cannot Encode, NSUnderlyingError=0x2819138d0 {Error Domain=NSOSStatusErrorDomain Code=-12915 "(null)"}, NSLocalizedRecoverySuggestion=Stop any other actions that encode media and try again., NSLocalizedFailureReason=The encoder required for this media is busy.}