I got same problem but in a weird way...
I started my car in the morning as a routine, i let it to turn on for almost 120 seconds and when on a lil acceleration it went on cng, it turned off itself. i started again and on converting to CNG it went off again even i pressed the accelerator to the maximum but as it convert on cng it the accelerator become dead, feels like there is no pressure in it, anyway i was getting late from office i switched it on petrol and started my journey. The distance from my home to office is almost 20 minutes drive. During the journey i tried several time to convert it to CNG (even at the speed of 80kmh) but all in vain, as i convert it to CNG the accelerator looses its pressure and rpm, speed starting to decreases so i had to convert it back to petrol.
But surprisingly on my way back, when i start my car in the evening and after converting it to CNG all went good and never faced this problem again. It happened 3 days ago and i havent faced the problem again.
Can somebody help me why it happened and how to prevent it if it happens in future. what would be the root cause of it.
Thanks in advance.