Are you certain that there aren't any brush errors in your map?
List of solutions;
1- Check for brush errors and problems in the hammer editor, fix any invalid solid structure related errors. (I think the shortcut was "ALT + P")
2- Make the func_rotating, "NOT SOLID". You can do this by checking that option from flags.
3- If making it "not solid" fixed your problem, but you still want the rotors to hit the players when they touch it. Build an another dummy and blocky rotor on top of your func_rotating, texture it with trigger brushes (except the origin of course) and make it func_rotating, Set rendermode to texture, value 0 to make it invisible. At the end you should have 2 func_rotating objects, one of them is visible with not solid flagged, and the other one is just invisible and hurts players when it touches.
If the func_rotating is too fast anyway, just place a trigger_hurt instead of an another invisible func_rotating.
But I strongly suggest that you check for brush errors in order to improve your mapping skills.