in a 4507 switch, I have 2 units of 4200W working in redundant mode. Each PSU has 2 input of 220V. Call it PSU 1-1, PSU 1-2 for PSU1 and PSU 2-1, PSU 2-2 for PSU 2.When PSU 2-1 input is faulty (power source and cables are fine, confirm is PSU hardwar...