1992 LEXUS LS400 FRONT L/H WHEEL WOBBLE

[artwalk]

This wheel wobble, which is a vertical wobble and is extremely violent requiring the car to be brought to a halt, is only intermittent, meaning once every 12 months or so. In the meanwhile the car drives perfectly, not a shake, wobble or vibration of any kind whatsoever. When it first originated 12 months ago (June 2016) I took it to a tyre retailer, Jax, in Bondi Junction NSW who performed a wheel balance on both front wheels, and a full wheel alignment. I then had trouble free driving for 12 months until now, June 2017. This current exact same wobble came out of nowhere and I stopped the car. I then drove on without any wobble whatsoever and have driven about 500 km since then without any wobble. Does anyone have a clue as to what this "mystery wobble" is? Particularly, as it only visits me now and again. Although the car is 25 years old, it has only done 126,000 km and is in perfect mechanical condition. I would welcome any input from the club or elsewhere if you have some idea what it could be. Thanks.