Hi, everybody. There is an error:
811 FCP IO link communication error 12400001

What was done:
1. replaced optical cables
2. Replaced the FUB-DR3 unit
3. replaced the FUB-P4M4 unit
4. replaced the FUB-P4R2 unit
5. reinstalled the system
6.checked all power supplies.

Please help, okuma representatives claim that the FUB-DR3 unit is faulty, but it was replaced with a serviceable one.
What else can I check? or what actions to perform?

Machine okuma LT-15 M, OSP7030, OSP-U100