Minecraft Version 1.12.2

Forge Version 14.23.1.2578

Mod Version 1.12.2-0.2.0-85

Describe your problem, including steps to reproduce it

Shift click on exposed PCB in UV Light box while unexposed stack is in inventory.
Observe that the exposed one joins the others, becoming unexposed.

Any other comments?

Other than how awesome this mod is? None.

That's actually fixed in dev already. There will be a new beta out soon, but you can try dev builds from http://jenkins.k-4u.nl/job/PneumaticCraft-Repressurized if you're interested.

And the official build: https://minecraft.curseforge.com/projects/pneumaticcraft-repressurized/files/2513548