HD textures for Banners do not work

When changing textures of banners located in "assets\minecraft\textures\entity\banner" of a Resourcepack, the textures do not work if their size is not exactly the same as Vanilla ones preventing HD textures.

If changing texture for Banners to new HD textures (with correct scale), no texture at all will be displayed in game leaving the banner the default color it was made off.

If changing texture for Banners to new textures of the same size, everything works as intended.

What I expected to happen was:
custom HD textures for Banners displayed ingame

What actually happened was:
custom HD textures for Banners invisible ingame (not displayed or not used)