Fault jimny fault shaking steering and gear stick please help anyone

H E L P

Please help video attached of the fault with jimny
Hi all this is my first jimny and bought this with a steering wheel wobble said to be wheels needed balancing....
It's a 2004 model convertible jimny 02 ..the problem is intermittent amd doesn't happen under 40 and untill this fault happens she dives fine through all gears .....
Fault
wen at highway speeds random times the wheel will shake from side to side it lasts 10 seconds but the gear stick shakes side to side violently as well ??
Diagnosis
Parts changed as was thinking it could be warped discs so changed them along with pads
Changed gear box tear mount as this was split and checked all tyres replaced one and had all balancing of wheels done individually .
Had the tracking done and the problem is still there but only at highway speeds
It's very random above 40 mph and nothing seems to trigger it as its done it without breaking but most of the time around town it drives a dream and it doesn't happen at one set speed

Video I have a video of this happening the sick slapping left to right is the mystery really gears are generally tight and box seems to be fine

Run out of clues now amd monie is running out please anyone can they advice what they think this could be..

I couldn't add video but anyone who can help I can send via email if you can send me it thanks

This is a mystery as I've had the local garage look under it and they can't find a problem with anything ?? . .?