I'd doubt that the rotation speed of a wind turbine would cause a radar problem.
Then you would doubt wrong. Wind turbines can and do cause significant problems for primary radars. The interference appears as clutter on the radar screens. The CAA is well aware of the issues, see CAP764 for details. Without effective mitigation, it may be necessary for controllers to apply both vertical and horizontal separation, particularly in areas where there is a mix of cooperating and non-cooperating traffic.
There are several windfarm mitigation solutions coming to market, each of which offers to resolve the problem.
S-D