I have a CM5.2 mixed digital and IP sets. The sets in question are digital display sets that are part of a pickup group and a coverage answer group. The question revolves around a flashing pickup light. I do not have pickup alerting active in my system features, yet these stations will see their pickup button fluttering . . . sometimes there is a call at their station (I am assuming it is there due to the coverage answer group) and sometimes there is not! No audible ringing during this 'unusual' time!