I have 6 S1s, a BE Cube and two BE Blades. I "think" mine was due to wifi as its back up above 1200 consistently. I don't watch the ants status page constantly, but they weren't showing anything different when they were down around 1160 as they do now when they are above 1200. (1220s average)
wifi can do lots of stuff like that. can you try using a electric wire cat 5 add on?