I've built in 'damp basements' for a long time and hated it...the wood would get 'mushy' and the plans were damp - UGH!

But to answer your questions, yes, unglued wood will warp, especially sheeting. But it seemed once the wood was 'fixed' into place, it stayed there. Of course when you brought your plane out of the damp basement into the warm sun, the covering was a wrinkled prune in no time.

Maybe the great humidity change caused some aerodynamic changes I didn't see and could explain the crashes....naw, it was pilot error all the way