Wa450-3 parking brake issues

So, this last week I was running my 450, using it to load a manure spreader. I'm a one man show right now, so I would load the spreader, then shut off the loader. It would typically take me 12-14 minutes to spread a load. When I fire up the loader again, I'm having difficulty getting the parking brake to disengage. If I flip the parking brake switch, it takes about 4:00 minutes for it to release. If I toggle the switch, then rev up the engine, it will go off much sooner. But it seems as though the warmer the machine gets, the higher the revs it takes. On a cold start, the parking brake will almost immediately disengage.

In the past 20ish hrs I changed the transmission fluid, and filter, and had the pilot cleaned too.

I was wondering if anyone had any insight into this.:confused:

Thanks, CJ

Wa450-3 parking brake issues