[rules-users] No activations created for condition with two checks for collection size

Hi, I'm trying to check the following condition: when $currentLowLimit : LimitViolationEvent ( limitTypes.size == 1 && limitTypes contains LimitTypes.ACTIVE_LOWER_LIMIT && parameterNames.size == 1 ) limitType and parameterNames are both Sets. I know events exists which satisfy the condition. But why are there no activation created at all? Thank you, Tina