I'd lean towards a jack down buzzer , if the sound stops when you shift to park.
B-in-L had a 05 Tiffin on Workhorse chassis and his , jack down buzzer, would go off after every fuel or lunch stop.
Heat from the exhaust would cause enough pressure build up in the hydraulic system to move a jack and trigger the buzzer.
Talked to HWH and their idea was to have him use the store button after every hot start up , after two mins the system shuts off, so you can just push store and drive.
Might be worth a try.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.