I'm going to agree the narrow chain is primary reason for skipping.

Also agree that almost all freewheels wobble. One source of that is bearing races with not enough balls. It's a large diameter race that takes a whole lot of little 1/8" balls. If the races are filled completely the FW binds. Best operation is usually two, three, or four balls short of full. At the factory this is not done accurately and they are always way short of full. All the way back to 70s I opened my freewheels, greased them and added balls. Doing all that work did reduce wobble substantially. If it bothers you go ahead and open the FW. Everyone should try it once.