To track, the HWH main pump/resivoir, have someone run the jack system as you track the noise. Do you have an HWH manual ?
Fliud level sould only be tested with all jacks retracted. A binding seal in the stuck jack is a possibility or weak return springs, and as the other poster says it can be helped up, another post has photos of a totter that a member built to do this without crawling under.
Sorry we were typing at the same time , actual location is at the "whim " of the coach builder.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.