Conversion code is not a script, it is included in qBittorrent executable. When a torrent is paused, there should be an error in the log though, with the reason for the error. I'm surprised that this is not present in your log. Are you sure you copied the log *after* the torrents were paused (due to error)?
I will have a deeper look into this particular code tomorrow and try to figure out what could have gone wrong.
