Part of your cycling system is the tappet/nozzle/bucking action area, so it's possible that it's cycling normally but not cycling "well", if you get my drift.
A few things to try:
- Secure your hopup unit tight against your gearbox, whether with tape, o-rings, or whatever. Make sure it's tight and not moving.
- Try a few other buckings. It's possible the bucking lips are too tight for a BB to go through, or too loose.
- Inspect your tappet plate and make sure the end that engages your sector gear isn't worn down or something.
If you are having BB-roll or double feeding, it can often result from a bucking that is either too tight or too loose, or a tappet/nozzle cycle that is whack, or something in that area.
Take your hopup unit and barrel out of your gun and place a BB up against the bucking lips. It should stay in place and not fall into the barrel. Now take a thin hex driver or a needle (I use a knitting needle) and gently tap the BB. It should fall into the barrel. Make sure the other end of the barrel isn't sealed when you're doing this test
edit: Problems like this can also stem from the wrong size nozzle. If you find that your compression is amazing in one shot and terrible in the next shot, it's possible your nozzle is too long or engages your bucking lips improperly (thereby making them act like they're too loose), slamming the BB far into the barrel before you actually take the shot, causing its travel distance to be shortened.