Triconex ESD DO MODULE# 3625 Fault (No communication on a leg)

We have been facing multiple DO card unrecoverable faults at our site. The model installed is 3625 (manufactured around 2011). In the recent years, the faults have increased to almost 5 or 6 times a year in multiple slots. As per EDM, fault description is given below:

"Communication lost on active leg of a board"

The fault persists once it appears and does not reset even on power cycle. Please let me know if anyone else has ever faced this issue and how we can rectify this problem.