@xuraax, yes saw ...
https://www.kymcoforum.com/index.php?topic=31322.0..and hoped you would get this issue sorted out by your dealership.
There has to be a reason for this behavior and eventually will be found.
Do you have a kill switch right hand?
If yes, is it possible you hit this switch assambly with something, scratches/signs there?
Take the met - in box out and try (motor running) WITH wearing gloves and rubbergloves over them, to bend/pull gently your ignition cable which leads from your ignition coil towards sparkplug.
Maybe some reaction
Try with idling motor to bend all other cables/ fuel lines, etc. Maybe reaction.
Pull on all ground cables (green).
Bend your air-intake pipe.
As a further measure I would (if the dealer cannot find the failure for month)
Install a external fuel pump temporarely and see how it does. Need not to be a posh one, off the rack from Amaxon or Ebai. With this I would see (clear fuel hose) whether bubbles or dirt is delivered from my gas tank.
If there would be an ECU fault, the tech should see a failure code in diagnostics.
If possible give us a feedback.