I also got this but only for two times in one month. When it happened I noticed that my priority 1 mining pools server went from alive to dead. A reboot solved the issue (miner resumed mining on priority 2 server and when server 1 came back alive, it switched to that fine with no problems). I think it may be to do with the firmware not coping with a server going down and switching to priority 2 server.
The first time it happened I was on the default firmware for the mid-Sept batch (17.5GH) and the second just happened yesterday and I am on the 20th Nov 2017 firmware (latest version at time of posting).