The following dax query will get you the last record from a related table.
_number_call_waiting_last_record_in_days =MAXX ( TOPN ( 1, FILTER ( IncidentDurationBlocks, IncidentDurationBlocks[incidentid] = incidents[id] ), IncidentDurationBlocks[end], DESC ), IncidentDurationBlocks[duration_inSeconds])
The following dax query will get you the last record from a related table.