For whats it's worth I've been running a fork of the syncthing android app for well over a year now and it's not skipped a beat.
https://github.com/Catfriend1/syncthing-android
Up to personal preference if you trust a fork for this work. But with sufficent backups I'm comfortable with it.
Can you share any details on the JBOD? How are you connecting it to the PC? I'd love something similar for my miniPC server.