While in the inventory screen on the preview the pattern appears to work perfectly but in actual third person the elytra appears as standard. I have tested with and without wavey capes (as they list an incompatibility) and without my shaders on. And I have no texturepacks that ought to be interfering.

Log included cause I assume it will be asked for.

latest.log

If you're using 3D Skin Layers, try enabling compatibility mode in its settings! It solved this problem for me. Good luck!