Update. Took it to a brake specialist - North Florida Spring and Brake - actually found them through someone in this forum who recommended them, hopefully they know their stuff... couple city fire trucks and vehicles there so hoping that's a good sign.
Anyway, the owner called me the next day and asked if there was something they had to do to move it because the brake wouldn't release... Told him that I hadn't had a problem with it releasing, just that the light would come on and I would hear the pump run every so often. Does it sound like a leak that has finally release enough to cause it not to release? I didn't notice any fluid dripping around the unit.
I'll keep you posted.
2011 Tiffin Phaeton, Freightliner, Cummins