Royal Enfield — engine off while riding petrol main state

Hi,
Recently i bought classic 350 redditch red and this bike had fuel issue.

While riding the bike in main fuel state, engine will get switch off after some distance. No problem in reserve state.

Serviced two times in re service center located in guindy industrial estate...

Still facing same issue. They are unable to solve it. Previously they told that this is known issue in most of bs iv model bikes.

Searching for next service center to fix it... Any suggestions welcome..