Hi I have heard there have been issues with the gearbox on the V100. A few Youtube videos are demonstrating a similar issue to what you have. While this might be classed as “normal” you shouldn’t feel an effect while riding, this is where normal becomes an issue in my mind anyway. 12cm is a lot of lash and I am not surprised there is a thud, I would certainly be taking the bike back to the dealer for inspection. With the different part numbers on the Stelvio compared to the V100 has MG not updated the gearbox to try and solve a few of the issues with the original V100 mainly the thud from neutral to first? I have a 24 MY bike so I don’t think I have the updated gearbox and while there is a thud when moving to first its not as bad as my BMW R1200RS was. I only have a couple of hundred miles on mine so not really in a position to compare but up till now the riding experience for me has been silky smooth.
Lets hope you get it sorted soon you will have to keep us informed of your progress.
Paul