Hot water heater bang

Think it might slide out enough to take water lines off ? Its a 1993 allegro bay 27' class c.

Sometimes it does ok. Sometimes it goes BANG when it lights. I just turned it on with no problem . it lights fine at first then when it tries to relight it happens,,sometime and sometime it lights just fine. Thay stuck this HW tank under the kitchen cabinet/sink area i have no clue how to get to the back side of the tank to take off water lines if i have to remove and replace it or to install the thermostat for the hot rod electric heating thing. No access pannel at all.

When was the last time you tried to turn it on? Is this the first ever?

Ok. I'll clean the burner tube. If that does not help, whats next ?

Too much propane is collecting before the igniter sparks it off. Like when you open the bbq grill valve and then the igniter won't light and then after a few tries it finally lights and BOOM! you get a big ball of fire in the bbq that singes your hair, if you happen to be looking over it when it goes off.

Bad air fuel mixture, or critters camped out in your burner tube. Start by cleaning the burner tube.