A picture is worth a thousand words...

Minecraft Version

1.16.5

Forge Version

36.2.0

Mod Version

2.14.6-277

Describe your problem, including steps to reproduce it

Build the largest pressure chamber to observe the not so connected textures for the glass.

Any other comments?

optifine installed as well, but connected textures from it disabled. Would the Connected textures mod cause problems or is that a required dependency for this one?

Closed due to lack of response

Try without optifine installed at all, please...

As far as Connected textures mod goes, it shouldn't have any effect - PNC handles connected textures for glass entirely itself.

No longer relevant, since latest version of the mod has completely redone texturing, including the pressure chamber glass. The CTM mod is now a requirement for connected pressure glass textures.

This happened to me when I don't shift click onto other glass blocks. It's a non-issue as long as I shift click onto other glass blocks.