that is scary....I do the same procedure with lighting the lighter then turning the valve, lid always open. The one thing that got me - waited too long to clean the stacks and drip pan. Went outside to find flames coming out of the left stack.
Char-grilled burgers were salvaged, thankfully. Just glad the grill wasn't next to a wall or it could've been real bad.
Great grills, not the best for a steak IMO but will do the job.