I find it hard to believe over lubrication will hurt much, other than packing grease, that stuff gunks up everything. Only two problem glocks I had were those lipsey cerekote fde pistols. Both gen 4, one a g19 and one a g26. I couldn't even get through a magazine without malf city, to the point I field stripped them and cleaned and lubed them and started again, still no luck. After about a hundred rounds through each they finally worked as they should. My guess is the cerekote was either too thick, or places it shouldn't have been. Coincidently both rust like heck now too that most of the finish wore off. I thought glocks weren't supposed to rust even being in salt water for a decade and all that stuff...? they rust almost as bad as my p365 now. I wish they didn't have to stop the old frying pan finish they used to have on gen 3, I don't remember any rust issues with that finish.