The safety add-ons are using only the event class ERROR, not WARNING. Events are not acknowledged automatically. After acknowledging an error event the error event is set again if the reason is still there.
One case which is usually hard to find is a short drop down of the compressed air, for example because of moving a big pneumatic cylinder or many cylinders at the same time etc. But also in this case there is an error message "Pressure present expected = 1". But after acknowledging it there will be no error anymore because the compressed air is present again. The default time is T#250MS to ignore drop downs of the compressed air. It can be changed in CpStudio/OES.
In combination with a SafetyValve add-on the parameter rIsCompressedAirOn of the SafetyValve add-on helps to see the correct error event:
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