Hello!
I constantly experiencing the same issue, torrent downloading (by magnet link) from time to time interrupts with the next message:
Permission denied: /storage/emulated/0/torrent//. Hard to predict when it happens, sometimes you may download 1GB before this issue happens, sometimes 10Mb. But always pressing "pause" and "start" again helps.
It's really annoying, as you have to constantly monitor the status. Fell free to get in touch if more details are needed.
Thanks,
Alex