It´s maybe a power problem with the hashboards,
when you run your miner at 120V reduce the frequency in adv. Settings, maybe to 500 or lower. when you have 240V try with 506.
has more to do with your psu than the (edit for INPUT voltage I mean) voltage you are running at.. pretty much 240v to psu vs 120v to psu comes down to how many amps the psu draws (how hot is the psu and the cord to wall going to get) psu to machine is 12v and whatever amps the settings draw, it doesn't give a flip at that point what the input voltage is. (240v is better for many reasons, but primarily (for miners) to ease the workload on your psu, and in the case of certain dual voltage psu's allow for more watts to be drawn (which also decreases the work load on your psu.) over half the problems I've encountered with people overclocking was about the psu and not so much the machines. - The other half was about improper cooling. (Either from manf end. or user derping)
All that being said lowering settings is still probably the right choice.

I think they are from the same machines, because the two I bought came with errors.
1 - It has an error in the 3 CHAINS, it is not active, it is active ... It takes 20 seconds with ASIC STATUS in "0" and ASICS is missing, and then everyone has the "X".
2 - You are in error only in CHAIN 1, taking only 5 ASIC STATUS.
I do not know what else to do...
You were already informed what to try, lower the speed. --> do 400 freq - see if the boards come back up, if they do cool .. work your way up, if they don't then come back with what they did when you put it at 400. Does that make it clearer?