Just got finished building a Glock 19. Everything works as it should. But when I go to put the slide back on. I have to pull the slide stop lever down. to get slide to go back on. Everything works but never had a Glock that you have to use slide stop lever to get slide all the way back on. It does have a Combat Arms match grade threaded barrel. All the upper parts and lower parts are OEM. Could it be the barrel? I have never used this brand and not sure if it is the problem?