Node guarding event cannot be reset (elimination)

Which products are affected?
EPL-10200 (Drive PLC V7.1 and lower)
EVS93xxEI (Servo PLC V7.2 and lower)
EVS93xxET (Servo PLC with technology function V7.2 and lower)

What happens?
In response to a node guarding telegram the PLC target system does not change the toggle bit accordingly. An activated node guarding event (C0168 = 260) can only be reset by mains switching.

When does the problem occur?
The response described occur may occur in case of a high bus load on the system bus if the PLC target system has been configured as Slave with node guarding (C0352 = 4).

Possible diagnostics?
None.

Short-term measures/recommendations?
None.

Evaluation:
The function restriction may occur in case of a high bus load on the system bus if the PLC target system has been configured as Slave with node guarding.