I have just received a brand new SS PPK/S from Walther to replace a previous gun that they couldnt repair. The new gun will not hold open with an empty mag. Not with the new mag sent with the gun, nor with (2) other brand new Walther mags purchased, nor with an older used Walther mag. Again this is a brand new (unfired) gun and new mags. Not used, not dirty. Any ideas? C.