I believe that rockets have a reset function on one of the models of poe.
It sends the reset signal up the ethernet cable.
If you have a fault in the ethernet cable, it could be recieving a reset signal. On the »forum.ubnt.com
there are some drawings posted about a year ago detailing how the reset function works via the ethernet cable. This may help you understand the issue.
The other possibility is that the rocket could be faulty.