Could simply be bad paint. Or a paint/barrel bore combo.
You said your LPR had both gold springs? One should be larger than the other if my memory is accurate. The larger one on the piston stem, the smaller one riding on the adjustment screw.
Make sure your asa screw isn't screwed on too far and blocking air flow. Those earlier stock asa's have only one small air hole inlet so flow could be an issue.
Your gun battery may not be any good. It may have enough voltage, but not be outputting enough current to keep up with demand. Try a fresh one from a new pack to make sure.
That gun probably has a lot of cycles on it. The regulator piston seat in the HPR or LPR or both may simply need to be changed. They do wear out over time.
Make sure your valve spring is seated properly, and not crooked.
My guess is it's the paint, or the battery.
It's all about the angles.