Air venturi 74 cu. Gun depressurizing via bleed

Good day all.

I jus got my 74 cu air venturi 4500 psi carbon fiber. Hooked it up and filled up nicely. No leaks. When however trying to bleed off the connection the bleed valve was very hard and slow to depressure. Gun ended up bleeding out through the valve.
Removed the safty screw and removed the bleed valve. Checked for blockage and replaced.
Attempted to refill gun. Same problem. Gun depressurizing through bleed.
The bleed valve is very hard to open under pressure .
Filled the gun using my scubba tank and no such problems.
Any thoughts?