Bottom half of secret door turns into full block

[OmeletteYouFinish]

Optifine?: yes
If so what version: files says 1.12.2_HD_U_C7
Does adding/removing Optifine affect the issue?: modpack won't work without optifine so I can't try to remove it.

As stated in the title, the bottom half of my secret doors always stay a full block. I can walk through them fine but it still looks janky.

The only way i've managed to fix it before is by placing a block of the same texture 1 back-left from each door.

Not a huge inconvenience to fix but for some secret doors it ruins the whole build cause when you look from below you see this garbage.