https://i.imgur.com/gB3YtpS.gifv
(^ GIFV showing the issue)

So this is what happens when I have shaders enabled in-game and try to chisel blocks.
The bounding box on the blocks are not showing anymore.
When I tried disabling shaders, funnily enough my game crashed, so I restarted it and went back into the world.
Just to see that the block(s) actually disappeared now, whereas they were there before?

Turning the shaders off manually before starting the game, then getting back ingame makes the blocks disappear as well:

Even with shaders completely off, chiseling a block ingame, then leaving the world and re-entering it makes it go invisible.

There's nothing happening in the console in regards to this...

• MC Version: 1.11.2
• C&B Version: 13.11
• Do You have Optifine: Yes.

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Update 1 (of a couple, probably):

So it seems there was something in the console in regards to Refined Storage not being able to call a method properly (intercompatibility with MCMultipart).
Reading through a few other issues on here, especially this one, I noticed that it could be dropping other TE data.
Removing Refined Storage brought the blocks back:

They persist after a world reload even!

Now, back to the shaders:
After enabling them whilst the chiseled blocks are visible in the world - same applies here: Even after a world reload:

The bounding box however is still not visible:

Another thing I noticed is that the "invalid placement" render is in a super bright color with shaders (though probably related to the shaders / Optifine):

I think that's all I could trace it down to...