We are on the same quest and having the same issue.
Prepatch 1.0.2 we started it, brewed the drink then click the button on the calculator, then the fused broke and we repaired them annnnd.. nothing. We are stuck. It says to brew it agian and we can't.
We looked around and noticed that Wendel was back in his base for some reason, so we went back and got him. He acted like we hadn't gotten him yet (all dialog was reset) So we brewed the drink once more, the fused blew agian, we repaired them again and poof - same problem. The button on the calculator doesn't allow us to do anything.
Really disappointing considering all the hard work we did to get this far and now we can't even finish the game...