Wheel wobble can be a pain in the arse. Its not always the tracking thats the problem. Balancing of the front wheels is needed to correct wobble, but, you can also have problems if the BACK wheels are out of balance. I would suggest that you have a 4-Wheel alignment and all 4 wheels balanced. Another instance for this problem is your brake discs. They may be very slightly warped and at a certain speed it may be just enough to throw a 'wobble' which you can drive through by going faster. Balancing is a very fine thing and everything has to be perfect.