I have just bought a 2017 Fat Boy with the later throttle with no cables. Problem is it is jerky at low speed and when hitting bumps in road. I have had it back to dealer twice and they are saying there is nothing they can do , does anyone have a solution ?.

Is it stock Fatt?

Even if it's pretty much standard they can be like that from new. They are setup with a generic tune. The best solution I think would be to get it on a dyno. If you are thinking about do any mods, ie air, exhaust or cams, then do that first, otherwise you would need to get it redone on the dyno again.

TPS issue maybe.  They give jerky throttle at low steady speeds - say 50-70kmh

Could be quite a few things, but we will never know.