Fail on backup to SD card in Linux Mint

[jonathanrschwartz]

Since upgrading to 13.7 donation I can't back up to an SD card. I tried once and got lots of errors re: sync.ff_lock. After that retries stall with error 'waiting while directory in use...' followed by 'lock apparently abandoned' with countdown for each main subdirectory, followed by some 'cannot read file attributes of [some file] EIO input/output error [stat]'
I told it to ignore the error, it did the compare, then when I hit 'Synchronize' it went through the countdown again before transferring the files.

All files have read/write enabled, directories have create/delete enabled.