This sounds like a problem with the "Ready Signal" from the E/R module
on Terminals 72, 73.1, 73.2 & 74 of Terminal Block X111
It is very often feed to a PLC Input and used as a
signal which when lost brings up a PLC User Alarm
such as you have indicated.
Find a competent Electrician for the following.
Isolate the Machine/Control from 415 Volt Main Supply.
Wait Five minutes for Stored Energy to Discharge.
There are usually two cables connected to X111.
Disconnect them from the E/R module and connect them together.
Switch power back on and startup machine as normal.
If you find this clears the fault you have a faulty relay inside the
E/R module. I've seen this a few times before.
I've never fixed or found the internal relay.
Just replaced the whole E/R Module.