See: FTBTeam/FTB-Modpack-Issues#7537
When crafting raw basic processors and certain other items, shift left clicking the output can dupe the ingredients. The issue is apparently gone when removing FastSuite.
Modpack Version 1.7.0

FastSuite only impacts the recipe matching pipeline, it doesn't mess with the actual crafting logic (which is responsible for decrementing the crafted items).

Does removing any other mods impact the result?

Hmmm, in that case, it might be introducing a race condition in another mod... fun.
We'll try to look into it but no promises from me, since the issue isn't consistent on my machine.