Several things could be aggravating this. Weight is one for sure. When you make repairs or when you build, think strong and light. Carbon fiber is lighter than wood. Also, as you add wood and tape make sure you are careful about wash-in and wash-out (these can drastically effect the stability of flight and cause the wing to stall easily). Wood tends to warp, as you well know, and gluing a warped piece to a wing or any other surface can warp the entire surface. Gorilla glue works well for me if you want strength, but I must admit I do not know if you can use it on foam.

In general it sounds like you have gone a little overboard with your repairs and mods.

Tom