Recreational Vehicle Lpg Tank Valve/gauge problems of the 2016 Subaru Forester

In a closed parking lot, I was getting ready to park in a space. With my foot on the brake, I cut the wheel to the right and then eased my foot off the brake to maneuver into the parking spot. I pushed the brake again in preparation to straighten the wheels and finish parking, no speed registering on the gauge. With my foot on the brake the vehicle began to accelerate and jumped. I lifted my foot off the brake, and slammed it back down on the brake attempting to halt the vehicle. Instead, with my foot still firmly on the brake, the vehicle accelerated again, and faster, right into a wall. I had been unable to straighten the wheels, so the impact was not head-on, but rather continuing the right-turn's angle, and impact occurred on the driver's side, front-end. 2 airbags deployed with a slight delay, causing severe bruising to my legs which affect my walking, and muscle tears causing severe neck and spine pain. Though I was wearing my seatbelt during the collision, it retracted when I opened the door, and we were unable to dislodge it when we had to move the vehicle for towing. To reiterate, while attempting to park the vehicle at minimal speed, the vehicle accelerated on its own, with my foot firmly pressing the brake.