SW6D acting up

Got the Suburban SW6D in my 2008 toy hauler. It’s a newer trailer to me. Since I have got it the water heater has given me issues. The trailer sat for a couple years without use outside when I got it. The water heater sometimes fires right up and other times takes 20 min to start as it goes into lockout mode after 3 attempts and then I have to try again and again. Once it does start it heats up the water all the way, but sometimes will not come back on when the water cools on it’s own. I have cleaned out the tube, cleaned the contacts that make the actual spark and flushed it and put in a new anode. I have ran the burners for a couple minutes on the stove before starting and it makes no difference. Any ideas on this? It’s the direct spark model, NO pilot light, NO electric mode. Only propane. Thanks