I have found a way to make my overlapping alarms to work correctly. I have 1 alarm at 6:30 that plays a radio station, I want the Boom to play a different station at 7:30 - this doesnt fire as it overlaps the previous, instead the Boom goes silent. If I have a "dummy" alarm at 7:29 which because of the overlap stops the first and produces silence for 1 minute. Then the wanted alarm is set for 7:30 and that works as it should. So it seems if you want the Boom to switch stations at a preset time you need to insert a dummy alarm.

This was not necessary with 7.4.0!