This scenario sounds a lot like what I went through a few days ago. Even though you mention a static IP, I suspect a dynamic IP instead. I'm only guessing here because I don't have enough info to say for sure if the IP is static or not.
But, here's what happened to me and my A3. The entire machine went berserk throwing X's all over the hashing boards. I unplugged it and eventually did a hard reset. I mistakenly thought it would preserve the IP address. But, I would not connect to the miner's web interface. What drove me nuts was the fact the miner was continuing to mine and I could ping what I thought was the IP address. I eventually turned to my main router connected to my cable modem and had a look at the DHCP Routing Table. Sure enough, the A3 IP address had swapped places with my ROKU box in the living room. I had been pinging and trying to connect to my ROKU. Ouch. Lesson learned.
I thought I might post an update. I just now switched back to the Siamining pool from Antpool. I let Antpool run for minutes shy of 24 hours on and I believe I made maybe 100 SC less. The A3 has been running for 10 minutes with both fans and temps in the nominal range. No crazy hashing board X's and only 2 HW errors so far. Fingers crossed.