It seems the issue is with breather pipe. People I have heard face same issues with few Balenos. As the tank pressurizes the Fuel pump loses pressure and car starts missing. It happens more when this tiny car is under AC and as the electric system is under load the Fuel pump performance is also compromised.
Remove the tank check if breather pipe is properly installed.
I have heard people punching a hole in the fuel tank cap or using some old cap.