PLC5 ASB module fault

Hello,

I have a remote IO rack communicating back to a plc5-40 processor via DH+ that has recently given me some strange issues. the rack has been in service for probably 15 years with no major problems. starting on 3/1/20 we had an adapter fault out of no where. Module got swapped and almost exactly 12 hours later we had an identical issue. The card we used to replace it was a used spare. the night tech assumed that it was actually a bad spare and replaced it with our last new ASB module. 13 hours after that we got the adapter fault light again. i mostly work on the hardware side but have some very minor programming experience. im at a loss for what could be causing this. Has anybody experienced a similiar issue before?

Faulty spares are absolutely a possibility.
Even brand new in unopened box, electronics age when laying on the shelf for years on end.
In particular electrolytic capacitors are destined to go bad sooner or later.

Three bad modules seems unlikely though. What is the status of the lights on the ASB module when the fault occurs?

OG

I'd be more suspicious of the "blue hose" and terminations after 3 in a row ASB faults.