I get the same reaction in quads and calfs no matter what or who's gear I'm using and seems much morse with water based like winny or test susp. I've tried all the tricks and no luck. I understand the hard to hit the ass with a smooth stick, aspriration, and pushing end of plunger with 3ml. It's not easy. Sometimes geeting someone to poke you makes it easier but is a pain in the as everytime you need that poke. Could be high BA but if no hurt elsewhere then I doubt it.
Have you tried biceps and triceps? I rotate from glutes, shoulders and if need be bi's and tri's. Don't want to try quads or calfs since I could not walk 4 days.
I might try higher on the quad and see how that is.