Try to flash it with newer firmware and maybe this will work. I'll tell you what to try:
1.Is your DHCP configured at antminer's side correctly?
2.TRY another PSU or plug only one antminer.
3.buy a clock switch
4.Our member of this forum had the same problem but his antminer was s1, so if you want look for that, who knows, maybe it will help you despite you have antminer s5.
Here is the thread's link:
https://bitcointalk.org/index.php?topic=588253.0Tried all sorts of FWs from bitmaintech..
1. Yes, its actualy a set IP, and the miner have been working fine until a couple of weeks.
2. Already tried it, switched to a HP server PSU 1kw, still same crap
3. yeah, im prolly going for it.
4. I´ll look into it
tanx