I'm really not too concerned because I believe this T.T. has some kind of a Styrofoam fused core curved roof - which likely has a lot of "soft" spots when you walk on them. I try to walk lightly when up there - disappointing, but not a need to "dump" the T.T. yet, unless someone knows better?
Any kind of soft spot, low spot, is rot. The wood has gotten wet and has started to degrade. This can be fixed but I would not use a self leveling sealant to fix it. You need to get under it and get rid of the rot first otherwise it will only ever spread. Then make sure everything that needs to be sealed is sealed good.