Most of our machines are built with an HMI page (WinCC 7.4) that is indication if any of the safety HW is not working so I can see the feedback signal of each of the safety I/O cards (f.ex. "F00680_FDI24xDC24V".QBAD).

If one or more of the cards are in error there is a button where I can activate reintegration of  the safety cards.

Most of the time this is working but sometimes it is not enough. The cards will briefly be shown as OK on the HMI page but soon after this they will indicate error again. That might indicate that the card(s) is defective but this is mostly not the case. If I give the PLC a warm start the cards will be OK again and the safety can be reset and production resumed.

Why is this happening and how can I modify my reintegration logic so that I don't need to give the PLC a warm start?