Deere 644H loader boom down pressure wont hold?

Hi guys, i need some advice. I recently bought this loader, it has 30 k hours on it but has a new engine and rebuild tranny and axles and it works like a dandy but for one thing.
As the title says, The boom will lift the machine of the ground but when releasing the pilot controller the pressure wont hold and the machine lowers back to the ground right away. I wonder what the problem might be.
The ride control also does not seem to do much. When testing it shows it works a little(boom jumps up an inch or so but per manual it is supposed to be a foot) I am not concerned about the ride control but the dealer says it could be involved in the boom down issue.
I can have a Deere service guy come out to check it out but they don't come cheap at $225/hr + mileage :eek:

Thanks