730 articulated, park brake won't release

[heymccall]

Friend is working on a B1M022** and if left sitting over the weekend, the parking brake won't release until one hose (not sure which one) is opened and reconnected.
Park it overnight and everything works in the morning.
Swapped entire 240-0678 manifold from working truck. Still no joy. 201-0950 definitely getting release voltage.

 

[BigWrench55]

Is this park brake operated by air?

 

[heymccall]

Nope. Spring apply, hydraulic release. Very much like the Meritor Durapark on F700 and F800 Fords.

 

[Nige]

Can you find out which hose they have to disconnect/reconnect.? That might give a clue.

Attached parking & service brake SysOp in case it helps.