sometimes / sometimes not.. hmm

This applies to multiple other things. Crafting the stone knife being an annoying one since the rock disappears the moment crafting starts, not finishes.

This is tied to another bug how actions can hang or fail in high lag environments(or sometimes completely randomly with no apparent reason). Pretty much the servers need optimization and possibility to support fewer players. At the present a 40 player server, that's full, is outright unstable. It's outright mind-boggling that Bohemia is pushing the limit to 75 players, where servers start choking at 20s. That 75 player test server in Experimental is nearly unplayable.

Other actions that may fail include:
Crafting a splint
Using a splint
Bandaging another player
Giving a saline or blood bag to another player
Testing another player's blood
Giving another player adrenaline or morphine

In extreme situations even bandaging yourself may fail, I've had it happen before to a friend. We were forced to leave the server, go to an empty one, where he was finally able to patch himself up.

If you get stuck trying to craft a stone knife, repeatedly tap X and C

I am having this issue on experimental .57 today.