CUP172 - REAR BRAKES - ONLY ONE RECEIVING FLUID

[CupRacer172]

I have read a few posts about similar issues but nothing quite what I need advice on.

My car was having new brake lines fitted and when I went to collect they told me only one line at the rear received the fluid. They thought it was possibly the brake valve causing the issue as they rechecked the lines and all were okay, but I arrived when to collect at that point.

My rears discs and pads were only changed in December by my local garage.

I'm drove the car back home (almost 2 hrs) and want to take to my local garage to resolve (they know my car as they did the rear brake discs / oil change etc) however what specifically does this model have different from the later 182's...anything? Has anyone had the experience where one rear line filled with fluid and the other did not?

Any advice is appreciated.

 

[BashRacing]

It’ll be the proportioning valve, euro car parts did stock them

 

[npt]

Spray some wd40 on the valve and work it up and down, most get sticky after a while.
The valve needs to be in the up position to get fluid through the valve, you'll only get a little if the axle is hanging down with car jacked up.
You can tie wrap the valve closed while you bleed it

 

[CupRacer172]

Spray some wd40 on the valve and work it up and down, most get sticky after a while.
The valve needs to be in the up position to get fluid through the valve, you'll only get a little if the axle is hanging down with car jacked up.
You can tie wrap the valve closed while you bleed it

The car had all new rear brake lines. The rsports specialist said they are sure the issue is a blocked valve - to the passenger rear, although the other rear brake was successfully drained.
I've read there's a valve between the wheels but that's all i know at the moment.