CCMS autoreaction assignment disappears / deleted

I am encountering an issue with the autoreaction assignments for availability monitoring using CCMS in my Solution Manager system.

I have setup CCMS Availability monitoring using CCMSPING in my landscape and I can see the monitors in transaction RZ20 and all data is being reported correctly. I have made autoreaction method assignments based on instance availability to the MTE's in RZ20 and these have even produced alerts as expected.

However, after some time, the autoreaction assignment mysteriously disappears from the MTE. The MTE simply shows that no method has been assigned. All other autoreaction assignments do not have this problem, this problem only occurs with Availability MTEs. Is there some event or monitoring segment method execution that could be resetting the method assignment for these?

I have read note 939616 on Auto-reaction troubleshooting, but there is nothing that matches this situation. The autoreaction assignments work and alerts are triggered, but the assignment disappears or is deleted from the MTE after a while [several weeks].