I have many glocks:

-gen 1 G17
-gen 2 g17
-gen 2 g19 x2
-gen 3 g17 rtf2
-gen 3 g19 rtf2
-gen 3 g19
-gen 3 g29
-gen 3 g29
-gen 3 g20 x2

gen 4 g17


Gen 3 has always worked fine for me, no issues with the gen 4 but I sort of stopped buying glocks by the time the 4 came out,