Factorio Forums

It's quite a simple bug.
You need a blueprint of something, doesn't matter what as far as I can tell.
Remove something from the blueprint via right-click.
Move your cursor outside of the blueprint window and hover over an entity. Like an assembler or furnace or whatever.
And the thing you removed will be reset.

You're using extended picker? Or some other mod perhaps. It's causing it by forcing the GUI to refresh.

No mods.
KatherineOfSky's Tasty Vanilla series ep 43 at about the 14:50 mark you can see it in action.
I'd record and post it myself if I could atm.
Edit: it seems to be more specific then I first thought.

I can't reproduce this. Does it still happen for you in 0.15.9?

I haven't been able to reproduce it since 15.8. Before I updated to 15.9 I was able to narrow it down to floors in the blueprint and logistics boxes in world. However it was temperamental, like there was another condition being missed.