Here is the guide to check the parking brake. It is what I use to find problems.
247B, 257B, 267B, 277B and 287B Multi Terrain Loaders and 216B, 226B, 232B, 236B, 242B, 246B, 248B, 252B, 262B and 268B Skid Steer Loaders Interlock Electronic Control System Media Number -RENR6417-01 Publication Date -01/08/2005 Date Updated -03/08/2005
Parking Brake Intermittent
SMCS - 4284-038
System Operation Description:
On some machines the parking brake will engage intermittently during normal operation. This can be caused by several components that are unrelated to each other. Components that can cause this problem are:
Park brake switch
Harnesses (cab panel, upper and lower platform)
Seat / arm bar switch
Main power relay
Power and ground connections (including battery cables)
Interlock ECM (unlikely)
Aux Hydraulic ECM is not tied to the park brake solenoid therefore can not cause the park brake to be set
Follow this guide and let me know if it leads you to the problem you are having.
I did find a service letter for your machine. It has expired and I don't see were your machine had this repair done. The dealer may not help much since this letter is two years old.
It replaces the park brake manifold.
Certain skid steer and multi terrain loaders may experience unacceptable service life for the parking brake solenoid valve assembly.
287B ZSA01287-02652, 2700-3895
1 each;(NNN) NNN-NNNNVALVE GP-MTG&
This is a one hour repair according to CAT.
Item #5:(NNN) NNN-NNNNMANIFOLD & SOLENOID GP-CONTROL (PARKING BRAKE)
If the guide doesn't point out the problem the valve may be the whole trouble.