O.K., if I have one of the duplicates in the Stasis Hold on the Bridge, then it stays when the equipped original vanishes.

If the duplicate is in the inventory, then original and duplicate vanish at the same time.

This bug got worse: This time I kept the duplicated Signum that I crafted, so that only one would vanish later.

Now both(!) the equipped one and the one in the inventory vanished.

It would be very nice if this bug could be finally crushed :-(

It happened again, this time I crafted a Main Implant and equipped it.

To see if I can get a better one, I started crafting another Main Implant and left the game.

Later, I came back and claimed the new Main Implant. When I looked into my inventory, there was a copy of my equipped Main Implant in the inventory (upper left corner), and the new one right next to it (to the right, so it looks like the copy was placed first, before the new one was put into the inventory).

I played for awhile, with the copy still in my inventory, and nothing happened.

Later I put the copy in the stasis-storage on the Bridge and left the game.

When I came back again, the equipped(!) Main Implant had vanished, but the one in storage was still there (so I equipped it).

That should be Starwalker as well, the character to whom this happened is named Tregar.