How to delete a thicken surface that is giving an error

I am doing a design for a senior design project, I want to change the windshield in the design to see if a full canopy gives a better drag force in a CFD analysis. When I try to delete the old windshield it says that this surface cannot be deleted. I tried deleting other surfaces that have been thicken on the car and it gives me the same error, I tried deleting sketches that I used to generate the surface but it still won't delete it. Does anyone know how to fix this or is it a bug that Solid Edge has?