From what I understand in your post, you have a 2 GPU's, and you consider that one of those is faulty.
let me clear first, why did you replace your PSU in the first place when it is mining without problems?
I was reusing some hardware from a old PC, and was using a PSU I bought back in 2009 and I was afraid because it's old so went swap it with my PC's Seasonic one.
Are your GPU's identical?
Both are GTX 1060 but from different brands.
did you try to install back your PSU? I am suspecting a PSU or a riser issues. so first in, try to install the faulty GPU alone using the old PSU in the PCIex16 slot.