[frizzen]

Sounds like you've either got some trapped air bubbles, or need to run a little more fluid keep from letting the pump push air.

Main boom rams are usually doubled up, and moving boom takes more fluid volume that the stick and bucket.

If it's got trapped air, you'll want to put the cylinder as high point in system, and crack a fitting open just enough to ooze or spit fluid until it clears up. Squeezing the piston shouldn't have any bounce.