AX 2012 R2 AOS and High CPU usage

Hi

Need little help with AX 2012 R2 and AOS that are using much CPU 75-100%. In DEV database there are lot of customizations and one day AOS begin to use lot of CPU, using constant 75-100% CPU on 4 cores.

Developers have turned off customizations but still when example forms are opened AOS starts to begin using lot of CPU.

When user close down AX client I can see under Online sessions that user have status Ending - Blocked, I cannot end session, the only way is to restart AOS.

Any ideas how to troubleshoot this?