Failed to backup with `scaninterval 0` (realtime mode)

[bluet]

When scaninterval set to a time, everything works fine.
But when it set to 0 (as mentioned in Document), it shows the error below and stopped backup.

UNABLE TO FIND WATCH FOR /some/path/to/file "/some/path/to/file": WRITE
UNABLE TO FIND WATCH FOR /some/path/to/file "/some/path/to/file": REMOVE

[bluet]

I also found that there's event listener failure of fswach.watch.add.subdir with no space left on device, but I have plenty of disk space.

[bluet]

not sure where the problem come from, so I also opened a ticket here jotta/jotta-cli-issues#148