Prince 5200 valve leaking

[igibson27]

I have a new to me log splitter with a two spool directional Prince valve on in. It's leaking fluid on the spring to center valve out of a hole on the rear face of the housing, under the end cap. I guess the hole is for a pressure release detent option, it's an unobstructed passage into the B work port so would be recieving full pressure with nothing to seal it aside from the retaining plate and centering spring.
This was a home built log splitter that was never fully assembled before I bought it, the previous owners had plumbed the hydraulics incorretly using the power beyond port as the return, I was not aware of this until I got it running and found the the valve to be leaking. This was a brand new valve and the parts breakdown has no mention of this hole. Any help would be appreciated.

 

[triptester]

The most common cause of leakage at the back of a control valve is a worn or damaged O-ring.

 

[igibson27]

Yes I assumed it was the oring and replaced it, but it's coming from a hole in the valve body. My phone won't let me upload a photo but the only reference I can find is on page 13 of the parts manual 'note 3'
http://www.princehyd.com/Portals/0/valves/RD5000Manual.pdf

 

[igibson27]

I finally took the end cap off the pressure release detent valve and there is no hole on that valve section, the caps were either swapped by the previous owner or came from the factory that way, they didn't look tampered with. Weird haha

 

[Jags]

From the breakdown it doesn't look like there is a matching hole on the cap, but it DOES have an o-ring for the hole. Is that in place (part 26 on the same page).