The Shield 45 is a little touchy on OAL with certain bullet profiles as the lands and grooves are tight up to the chamber.
I would remove the barrel and take a box of the ammo you are using and try the 'plunk' test to make sure the ammo drops in and does not stick at all when coming out. Could be an OAL problem, bullet profile problem or crimp issue. Make sure the round sits flush to hood of barrel or ever so slightly below it.
Karl
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