I've noticed while using the chisel the overlay was "depth fighting" with the texture its on, I read some of your posts and answers to other people on forums. You suggested that it was an optifine issue and yes it is but its not about the hardware age for sure, as I'm on MSI GE72 2QC with GTX 960m.
it was a config in the options that came with Optifine under the name of "Performance/ Fast Render" it appears to be changing the render algorithm which causes conflicts with your rendering.

I'm not sure if this was fixed, or was known to you i just felt like I should let you know just in case. Otherwise you can decline/remove the issue.

p.s. I'm using the latest version of your mod, and optifine 1.7.10 HD D1.

Generally the multi-core features in Optifine cause a multitude of rendering issues when used in conjunction with this mod. I don't know the technicalities behind rendering and what causes the issue behind-the-scenes, so the most I can say is to try single-core settings (if that's what it is called).