AB safety digital input card channel going to fault

[doomsword]

I have two cards (IB8S/B) on which safety input channel goes to fault about once per day (point status goes to 0).
Inputs are related to two estops (one of double NC contact) and only one contact per estop goes to fault.
I have to either open fuses or actually hit an estop to return point status to 1, after which I read 1 on NC of estop (as is always, I don't believe we actually lose 24V).

Right now machine is not running so I can easily do this but soon I won't be able to do that.

What might be causing this, what should we check for? Anyone had similar issue?

 

[Basti504]

We had a similar problem as well. Turns out you need to check the production date of the IB8S card, it is printed on the sticker which is on the side of the module. There is a problem with cards in a specific production range that might cause issues. I actually seen this in the field happening where we installed a line with +/- 120 IB8S cards.

See this technote from Rockwell: https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1132179/loc/en_US#__highlight

 

[JTCat]

Absolutely. We had some IB8S's that would not allow the machine to run if the processor was powered completely down and brought back up.
We had to unseat and reseat them to get them to work.

They worked 100% of the time until power cycled, then this would happen every time.
We replaced them all with brand new ones and haven't had the problem since.