If you have a full inventory and place an ore block in the fine manipulator slot, then shift click it out, the item is duplicated. This is bad news on servers.

what version are you using?
what other mods are involved?
is it only happening with ore block?

cyberware-1.12.2-0.2.11.26.jar (latest 1.12)
I am running the jojovein modpack, but there are no mods which actively change inventory interactions to my knowledge, the closest to that is Quark, and that has buttons and specific keys.
It apparently happens with any block that can be broken up into multiple outputs (as in more than one in quantity, like a compressed dirt block or ore block)

There's a lot of mods in that pack that interact with item, recipes or workbench. You need to find which other mod is causing that faulty interaction. Once you've that mod, we can see how it can be fixed.

Any update on this?

No update for 5+ months, assuming fixed.