AB Compact Logix PLC 1769-L24ER-QB1B High failure rate

[kbradio15 0]

Been seeing a high failure rate on these PLC's on 2 of our processes. The control power is feed through a APC UPS to a 24VDC power supply to power the unit. Getting a hard fault where the OK LED comes on red and stays red. It never sequences through all the LED on power up. Tried the hard boot by holding in the reset button and applying power. Has anyone on else seen a high failure rate on this model PLC? TIA..

[Olly_J 5]

Not sure but manual says when OK status indicator is Red:

"The controller detected a nonrecoverable major fault and cleared the project 
from memory." 

I suggest connecting to it via USB while the OK status indicator is Red and try to see if you can find the fault code when attempting to go online Studio 5000/RS Logix 5000 or pull it up on RS Linx/FT Linx and go from there.