ANTMINER s3+ 1 asic chain not working

[opasch]

Hello all,
I have 2 ANTMINER s3+ miners.
On one of them I got almost half the hashing power since a few days, 226 GH/s.
I compared the miner status screen of both miners I own and I noticed that on the one with problems I got a series of xxxxxxx instead than oooooooo from the working miner on the second asic chains, as shown in the attached screenshot.
I did already restart the not properly working miner.
Any suggestion?
https://i.imgur.com/cF8N11V.png

[opasch]

I am only wondering if it could be the fact that I am powering up only 2 of the 4 available PCI-E connectors.
This, though, should be a supported featues (to use only 2 of 4 connectors) as far as you use a powerful enough power supply as I am doing.
Any other comment on this?