The KTM 390 Adventure X will make for a good upgrade over your current Royal Enfield Scram 411. What you've mentioned about the KTM's electronic niggles can occur. However, these issues are sometimes sporadic and can also boil down to how you clean/maintain your bike. By and large, you should be okay with the KTM in the long run. 

You should also seriously consider the Royal Enfield Himalayan 450 because it has a proven track record, by and large. Also, it has far fewer electronic aids than the KTM, which will also mean fewer things to go wrong. 

The Kawasaki Versys-X 300 is a stone-simple machine with only dual-channel ABS in the name of electronics, and it will be by far the most reliable machine in the long run. However, this bike thoroughly feels its age when ridden against the competition, and it only comes with wire-spoke wheels and tubed tyres, which will make fixing a puncture quite difficult. 

The TVS Apache RTX 300 is a phenomenal package, but it is still too new a platform, and you'll have to wait and watch what owners say about its reliability. 

Small fixes like thicker grips or heavier bar end weights will provide some relief for the vibration issue on your KTM 390 Adventure X. You can also look at handlebar dampeners, although that will be a little on the expensive side. 

Another option you can look at is changing your sprockets to change your gearing so that the zone you find yourself in the most is as buzz-free as possible. Do bear in mind that putting an aftermarket sprocket could void your warranty, and we'd best advise you not to do so on a brand-new machine.