Hi, first sorry for replying and commenting in english. Its only because my German writing isnt perfect... I have similar problem on my 2018 1290 SA-R.. Also tried different tyres...
Between 60-80 my front wheel is bouncing up and down, and when braking from 40 down the front becomes unstable like nothing I have ever tried before.. So far so good (or not). Went to the dealer who measured the front wheel and clearly recognized the problem, both up and sideways uneven.
But from here on the problems starts, KTM refuses to recognize this as a problem... I see some of you have got this sorted on Guarantee, but I hear from others that KTM and warranty has become an issue. They might be growing too fast to handle customer complaints, not sure though.
All in all its extremely disppointing. Love my 1290 SA-R but if this can be solved it will bring me to a competitor of KTM.
For info: bought my KTM in Denmark where I live, but all service and above mentioned inspection was done by a very good KTM dealer in Germany.