Yes...most rotors have a pot inside which provides graduated resistance to
make the direction indicator needle work.
Chances are good that's what's wrong with yours. If you decide to disassemble the rotor to check that pot do your dis-assembly inside a cardboard box or plastic storage tub. It is often the case that ball bearings go everywhere when the case is pulled apart.
I have heard bad stories about Yaesu rotor support ans even worse stories about getting parts and/or schematics. You might want to call or email Yaesu before you start the project. I don't believe the domestic rotor repair guys (Norm's et al) will work on Yaesu rotors. But it can't hurt to ask.