Try adjusting the height of the pickup so the treble side is slightly higher than the bass side.
Is it a 2 or 3 band model? If 2 band, just remember that the bass control is boost only and, if you ramp it up you’re effectively cutting the mids, which is where your G string exists. If you’re doing the same on the EQ on your amp... bye bye G string.
The amount of Stingrays out there with stock pickups suggests the pickup design and manufacture is ok. I’ve owned a 2 band and a 3 band model, all stock, and never had this issue. I tend to bypass amp EQ on basses with a pre-amp. Try the same and see how you get on. Start with the bass control (on the bass) all the way down and the treble (which cuts and boosts despite no centre detent) around halfway. That’s the natural sound of the bass. See what the G string response is like and then start EQing to taste. It’ll let you know for sure where the G goes missing.