We have multiple g120c drives controlled by s71515 plc via profinet. Using standard telegram.

The drives R1 output is configured to control the motor brake.(Drives relay switches a contactor which in turn switches the brake on and off).

At Random times the Relay of the drive doesnt switch at all from closed to open or open to close.

At other times there is a few second delay between the drive starting or stopping and the r1 switching.

The brake settings are left at default values.

When this anomaly occurs i have to connect to the drive and just change any value (for example the delay open time to a different value, lets say from 100ms to 150ms) then magically it starts working again.

I started to think maybe it could be issues with profinet but the drive itself is controlling the brake, and the drive does stop and start when controlling it from the panels hmi.

Running out of ideas here.