my doors are flexing (in a not so good way)

I made my doors the same way I made my walls:
3/4" frame (oak), pocket screwed together
1/4" exterior plywood skin, titebond III and staples
1/8" interior luan skin titebond III and staples
CPES (3 coats on exterior), rolled
UNIFLEX 255 Aliphatic (3 coats on exterior), rolled
Polyurethane (3 coats on interior), wiped on
So, I put weatherstipping (3/8" in a 1/4" space). Worked great initially. Now, the door is warping or bending away from the latch slightly, but enough so I can see light around the top of the door, thereby meaning the door is no longer waterproof.
I can go with a 1/2" seal, but my concern is the door will just warp more. I am thinking about re-making the doors with a 1" frame. Before I go to that much work, does anybody have a better idea?

3/4" frame (oak), pocket screwed together
1/4" exterior plywood skin, titebond III and staples
1/8" interior luan skin titebond III and staples
CPES (3 coats on exterior), rolled
UNIFLEX 255 Aliphatic (3 coats on exterior), rolled
Polyurethane (3 coats on interior), wiped on
So, I put weatherstipping (3/8" in a 1/4" space). Worked great initially. Now, the door is warping or bending away from the latch slightly, but enough so I can see light around the top of the door, thereby meaning the door is no longer waterproof.

I can go with a 1/2" seal, but my concern is the door will just warp more. I am thinking about re-making the doors with a 1" frame. Before I go to that much work, does anybody have a better idea?
