Absolutely love this mod, have been using it a lot recently. However there is this annoying bug where only in a certain area, chiseled blocks seem to disappear gradually over time like leaves do when you cut down a tree. I say that they seem to disappear because they are still apparently there, and I cannot walk through them but I jitter whilst attempting to do so.
I currently am running on 1.8 Forge, with 15 mods active, including Optifine-1.8_HD_U_H5, which may be the problem.

I think I have found what was causing the problem. OpenComputers was causing other errors while I loaded worlds and so I have just disabled the mod and all the missing blocks are back [Yay! :) ]. Still, this issue should not go unnoticed and should be taken into account.

Carry on with this great mod!

It might also be Optifine, unless you have changed the dynamic rendering settings, or if optifine has fixed the crashes with the C&B Multithreaded Rendered.