SerialWriteTimeout on FEE

What does this mean? Fix it.,

{{
pfs@PFS-WS2:/data/pfs/logs/actors/ccd$ grep SerialTimeoutException 2016-12*
2016-12-01T08:29:26.log:2016-12-01 20:09:18.425Z cmds 20 CommandLink.py:120 > 1 2790 f text="command failed: SerialTimeoutException('Write timeout',) at /home...
2016-12-01T08:29:26.log:2016-12-01 20:09:18.430Z cmdr 10 CmdrConnection.py:53 read: .ccd_r1 2790 ccd_r1 f text="command failed: SerialTimeoutException('Write timeout',) at /home/pfs/anaconda/lib/python2.7/site-packages/serial/serialposix.py:505"
2016-12-09T07:12:00.log:2016-12-09 15:40:37.168Z cmds 20 CommandLink.py:120 > 1 12116 f text="command failed: SerialTimeoutException('Write timeout',) at /hom...
2016-12-09T07:12:00.log:2016-12-09 15:40:37.170Z cmdr 10 CmdrConnection.py:53 read: .ccd_r1 12116 ccd_r1 f text="command failed: SerialTimeoutException('Write timeout',) at /home/pfs/anaconda/lib/python2.7/site-packages/serial/serialposix.py:505"
2016-12-15T07:12:09.log:2016-12-15 20:59:44.590Z cmds 20 CommandLink.py:120 > 1 35758 f text="command failed: SerialTimeoutException('Write timeout',) at /hom...
2016-12-15T07:12:09.log:2016-12-15 20:59:44.592Z cmdr 10 CmdrConnection.py:53 read: .ccd_r1 35758 ccd_r1 f text="command failed: SerialTimeoutException('Write timeout',) at /home/pfs/anaconda/lib/python2.7/site-packages/serial/serialposix.py:505"
}}