How long have you had the replacement? Is it possible it may be a "pre-fix" unit? Then, it would be expected to be the same dimensionally.
I checked to see if something was under it. No, there wasn't. I believe that the window, the glass of the window, is not mounted correctly. The cut in the sight is right. It's the bottom edge of the window that cuts into the sight line. I moved the dot out of the way for demonstration purposes. Otherwise, the dot is right on top of my (usually, fully visible!) front sight...
It is entirely possible (and most probable) that my now working dot, is just a mis-made, misshapen, mistake...again.