Steps to reproduce:
Use any of "Template Module Interface (Simple) SNMPx" against a snmp server with network interface which generate errors once. Look at the trigger "Interface {#IFDESCR}: High error rate"

Result:
Trigger sets
Trigger never recovers

Expected:
Trigger sets
Trigger recovers after value have been constant over x minutes

Reason:
This is due to the fact tha ifInError and ifOutErrors are always increasing numbers. Not current rate of errors. Thus they will never go back down to 0 until the server has reset. The trigger should instead of avg(5m) just use an offset into history to calculate the errors the last 5 minutes.