The Royal Enfeild is a very old design. The motorcycle is based upon an old British design from World War II and has changed very little over the years. I do not know what type of quality control process the Indian manufacturing of the vehicle has implemented so that is very difficult to asses.
It sounds like your gas cap vent or your fuel tank vent is clogged
What you are describing is making me think that your fuel tank is not allowing atmospheric pressure into the fuel system.
Your gas tank has a vent that allows the negative or positive pressure out of the system. You may have a kink in your ventilation hose. If the gas tank ventilates to the atmosphere it may have blockage there.
There should be a vent hose that is routed all the way down to the bottom of the motorcycle. It would route behind the engine. This tube cannot be kinked.
The symptoms of kinked fuel line will be stalling after the engine runs for a period of time and consumes fuel in the gas tank. As the fuel is consumed the fuel level will drop in the gas tank. The dropping fuel level would create a negative pressure inside the gas tank. The vacuum would prevent fuel from flowing into the carburetors making the engine stall from being fuel starved.
Find the vent hose, you may need to take the gas tank off the bike, and ensure it is properly routed. If you find a kink in the vent hose, un-kink it and make sure that when the fuel tank goes on the vent hose doesn't get folded in half.
This may not have anything to do with manufacturing quality. It may have something to do with how the bike was assembled.