I'm working on making a set of advanced trapdoors for my rocket on a modified Tekxit 3 LE server, mod list below. I started with a grass block, then cut and added other little blocks to the bottom. After I finished making the door, the grass portion randomly comes in and out of visibility. I could be doing absolutely nothing and it appears or dissapears, or I could place a block next to it and it will appear. While open or moving, it's all visible and working correctly.
When I didn't use optifine, all little tiles would go invisible after leaving line of sight to my player, so I decided to put my effort into getting it working with optifine. I have render regions disabled, VBOs enabled, and mipmap on.
Was redirected here after commenting on the curse page. I don't use git much at all, so sorry if I did anything incorrectly in this post.

EDIT: oops forgot in game screenshots

Should be fixed in the newest pre-release. If it still occurs somehow just let me know here.