Recreational Vehicle Lpg Tank Valve/gauge problems of the 2020 Hyundai Sonata

The vehicle's fuel gauge (type c) does not accurately adjust for changes in the amount of gas in a timely manner. It normally takes 2-3 days for the gauge to move to full tank even though it is full. Same problem from 1/4 to 1/2 tank, etc. For example, I noticed the panel said I had 11 miles to empty on Friday. The gas gauge showed otherwise. I wasn't near my usual fill station, so I put 5 gallons of gas in the car. It is now Wednesday (5 days later). The gas gauge moved slightly yesterday to almost 1/4 tank, but the fuel tank warning went from 11 to 0 miles left to empty (see attachment). I drove on the highway each day and in the city. I purchased this car July 2020 with a full tank. This problem became evident in Aug 2020. After refilling the tank, the reader showed 111 miles to empty. I informed Hyundai agent of the issue, who had no idea why this was happening. The guage and fuel tank reader finally adjusted after about 3 days. I had 449 miles on the car at that time. I now have over 4,000 with same problem. Apparently, something is faulty, but I don't know what. Auto dealer is baffled. This issue could result in a real fuel shortage while traveling with no gas station nearby.