Our stove has had a couple small explosions due to opening the door too quickly after just loading it, however, it has never lifted the top off of the stove. I have noticed after looking at a few Jotul's that on some of the stoves the top of the stove where the top sits on and seals to, has variations in height. For example the back and the front cast is at a different height than the two sides of the stove. I have looked at both the 507 and the 507b Jotul's and on every 507 the top of the stove is the same height. On every 507b I have seen, the back and the front pieces are slightly higher than the two side pieces. I don't know why, it is not like the front and back are lifted off of the base, they are just higher. I had to go look at my three stoves and both the 507b stoves are identical with the front and back cast being slighter higher than the two side cast pieces. My 507 is perfect across the top. Other than my three stoves I have looked at four 507b Jotul's and one other 507 and found the same results with them. It seems that when they were making the 507b units, they lacked in the quality control area in making sure that all the pieces fit together perfectly as they did in the older 507 units. The different height of the cast makes it harder to get the gasket on the top to seal to the top of the stove. Maybe coalkirk can add some input to this and let us know if his Jotul is like this.