I’m mirroring the back part of the sleeve, which I’ve used control points to make the curves.
At the wrist edge, I’ve created the curve using the Curve with Control Points tool and this mirrors beautifully.
At the sleeve cap, I’ve used the Spline With Control Points tool to create the curve to move through various points. I’ve tried a number of times, but this curve refuses to mirror for me. Is this a bug? Or am I missing something?
Here are the files, if anyone would like to check: