https://bugs.winehq.org/show_bug.cgi?id=39602
--- Comment #10 from mazhe@alkumuna.eu --- The problem with that launcher (and later, the game itself) is that it tend to catch errors under very generic dialog windows...
This is most certainly not in the same category of issues. I managed to build wine under linux with -UNDEBUG and did NOT reproduce the js_copy issue. Linux's errors seems to be network related, while this one comes from javascript (but not wine-gecko?).
At that point, I'm not sure where to investigate: to be fair, building with -DNDEBUG seems acceptable and I'm more concerned about fixing later issues that I understand better...