Even Ultra_D3 does not correct issue from sp614x/optifine#60
Happened only on Win XP. With both chiselsandbits-12.getTileEntitySafely-extra.jar or just 12.7
(Don't know, can you reproduce it, but it's stable for me)

My minecraft intallation is so bizarre, heh. Uhhh...

CTM? as in the method for how Optifine / Chisel renders its blocks with different versions?

As for why you have an issue with windows XP I have no idea, but i can say I have no intention in supporting a version of windows that is 16 years old.

I also do not actually support optifine, i have gone out of my way in the past to try and get it to work with optifine in the common case, however this is just ridiculous.

Just in first looking i suspected only chiselsandbits-12.getTileEntitySafely-extra, but it's not.
Right, wrong way.