USB drive problems

[jgm]

I have permanent timeshift saving to a 64G usb drive formatted as ext3. This works for a time but after a while, the mount changes from:
/dev/sdb1 on /media/usb type ext3 (rw,data=ordered)

to


/dev/sdb1 on /media/usb type ext3 (ro,data=ordered)

My image is OpenPLi-unstable-vuduo-20100901.

Is this a problem with the drive or something else?

[jgm]

I'm also seeing this message on the screen:

Creating Hardline to Timeshift file failed! Filesystems like FAT32 do not support hardlinks!

[Errnno 28] No space left on device


I don't know where this is coming from, and I don't have a FAT32 filesystem