My Shield .45 also will make some " strange " markings on the brass... but it ALWAYS goes bang when it's supposed to.

I still use the .45 Shield as my EDC and it has been a gem. I have never once wished I had kept my 9mm Shield. I do sometimes wish these little devils had the material and quality build of my previous S&W 659 pistol, but I do NOT miss the heavy beast as far as operational sweetness.
The Shield is actually more accurate and satisfying for ME and FAR nicer to carry. Never had any malfunction type issues at all, even wet and dirty and nasty. My only problem is I don't SHOOT enough these days!