Oil Cooler Valve Assembly - Socket Keeps Slipping

[TLCStonks]

I'm pretty sure this valve is 32mm but I can't get any sort of torque on it without it slipping. Does anyone have any tips on how best to get this off?

I have no clue if it matters but it seems like there are two different types with different part numbers. I have a 2007 if it makes any difference.

15695-50010
15690-70010

Thanks

 

[3_puppies]

grind the socket flat, there are bevels inside the socket, get rid of those so the socket makes good contact
also a 6 point socket is best

 

[TLCStonks]

I don't have my grinder here but I order a "Chamferless" socket. It's flat and this one is made for mountain bike shocks but it looks very similar to the shallowness of the valve.