I've had that problem.
I've never figured out how to fix it in the moment.
I do know that oiling the iron is a recipe for disaster.
I do know that too much sugar in the batter will burn it before it's fully cooked.
I know that trying to open the iron before the waffle is ready is asking for trouble.
Making anything gf is going to take trial and error. It just is. Add in the altitude problems and you're going to have to really rock your T4 and tweak and improve your system until it's right.
I've discovered that a little less sugar, and a little longer wait time helps. If the iron has an adjustable temperature knob, you want it a little less than maximum heat. Otherwise, watch the steam. When the steam slows down to a tiny stream that's when you open the iron. You don't want to wait until there is no steam (like you would with wheat) because then you can't chew the darn thing.
I've also found that they get soggy if you put them on a plate right away. Try a cookie cooling rack.
I am certain that gf waffles are even better when you re-toast them the next day, but E-Bug can't agree with that. The boys don't care. If they get their waffles (or as Goggle says, "faffle") they're good to go.