Thanks for the report. I can already see how I managed to make this mistake without even having looked at the code yet. I'm sure the logic for enabling the craft button is only checking each ingredient, and since you have 1x Wurzeltrank, it's passing the check for each Wurzeltrank, because it has no ability to earmark the first one as being used already. That should be fixable for sure.
Cris also reported a couple of other problems yesterday, so I'm gonna try to fix them all today, if I get the chance.
~Ramza