I would send it back, with the mags.... and make a call to the center manager to explain your issues and lack of resolution. They must make it right. The Shield 45 design functions just great for almost all of us, so the center's job is to make your pistol function properly or replace it. I would want it replaced if'n it was mine, along with testing prior to shipping and a message from the center manager to that effect. This is a defensive weapon and MUST be stone reliable as well as effective.
Mine works great, and I would not accept anything else.

YMMV