SIGs are well known to be unforgiving to those who ride the slide release. Make a conscious effort to move your thumb a titch. That's all it is.
I ran SIGs for several years. My favorite handguns. Have owned a flawless pair of M11s. I just shoot Glocks better. If you run a SIG well enough, stick with it. Absolutely outstanding guns. Yours will be as good as anything out there.