AO880 modules failure during modulebus redundancy check

Hello All,

In one of our project we are using redundant PM867 controller with SM812 with redundant IO modules. In this scenario when we perform modulebus redundancy check by failing one modulebus link the functionality works fine (i.e no failure of any IO module.

However, only in one cluster we have two redundant AO880 modules. Only in this cluster when I disconnect one Modulebus link both the AO880 modules go to fault state while other modules AI880, DI880 and DO880 are healthy. In other clusters where only one redundant AO880 module the same issue does not occur.

Any help is greatly welcome.