SM idle problem

What can cause and sm from to idle and then register every 30 mins or less?

i have 6 sm registered and 4 out of the 6 keeps registering the other 2 are fine

this is a 900 intergated AP running P9 10.3.1 firmware

also on the same tower i have 5.2 ap software that has not issues and this tower is recieving sync from the SyncPipe

What are you signal strength/jitter, link tests and noise floor like? Have you power balanced your SM’s?