Good question

I don't know if you can bend coplanar waveguide, but I expect you can. Bends in microstrip also have reflections, and right angle bends need compensation, such as mitres on the corners, to reduce the reflection. Even radiused bends can have significant reflection if the radius is small. So it doesn't surprise me if coplanar waveguide behaves in the same way.

It is also worth checking whether there is a mistake in your model.

Malcolm White Thanks a lot! Changing the curve radius helped.

Good question