i had made this piece and wanted to mirror it as I felt that would be the best approach when dealing with a piece like this but when I try it’ll tell me “operation would result in invalid curve”. I haven’t been able to fund the curve in question leading to the error, so any help would be greatly appreciated. Here is also a link to take a better look at it Shapr3D - Project
You could try the workaround way by selecting all the curves you need > change to front or back view > click copy badge > center pivot point and rotate 180 degrees.
If then, you’d like it to be 1 sketch, you can project the new sketch to the old one.
This is a work-around, but it might help you in meanwhile, untill you find a solution for your invalid curve.