rsync doesn't delete files on OSX

I'm having trouble with rsync 3.1.2 on OSX 10.11.3.

The following script does transfer files but does not delete anything, which then gives me a full hd.

rsync -aE --info=progress2 -W --delete --exclude '.DS_Store' --exclude '.fseventsd' --exclude '.Spotlight-V100' --exclude '.TemporaryItems'
--exclude '.Trashes'  '/Volumes/840PRO/' '/Volumes/bk840/'

Gives this:

12,446,814,504  12%  179.55MB/s    0:01:06 (xfr#1104, ir-chk=1063/12094)

rsync: write failed on "/Volumes/bk840/LR/2013/SESC Pompeia - BigBits/time lapses/time lapse 1/DSC_4751.NEF": No space left on device (28)

rsync error: error in file IO (code 11) at receiver.c(393) [receiver=3.1.2]

rsync: [sender] write error: Broken pipe (32)

What am I missing?