timeout between processor 2 and i/o processor 2 in SLS1508

Dear All

I have Deltav with 14.31 lts  version

8 red dcs controller

4 red ESD controller each has 12 to 16 red SLS

today I've got this "  error timeout between processor 2 and i/o processor 2  "

and I lost redundancy and the standby one has red led

I tried to restart from diagnostic app. but after power up it keeps flashing for some time then gave the same error

Any advise will be highly appreciated

I do not have Guardian for this system

I have spare one and can replace but I want to make replacement the last choice

System has been  up and running since may  2020  

Thanks