I'm Dutch and I did this just to see how good my English to Dutch translation skill is and I noticed that 'We' as in the synonym for 'wij' isn't accepted. It's commonly accepted just as 'jij' and 'je'.
I would love to know the reason for this to not be included since it's even accepted in one of the main dictionaries of The Netherlands (Van Dale). I'm not sure if this can be noted as mistake, but maybe some sort of misunderstanding.
There is no confusion, both we and wij are accepted everywhere in the course. I just checked and this specific sentence is no exception. Listening exercises are treated differently by the system as explained by beloeng. When spoken by the text-to-speech (TTS) we and wij are clearly pronounced differently (as they should), I haven't come across any example where I would be in doubt.
Is zwak here the same as physically weak? Or is it closer to tired or exhausted ? The sentence 'we work until we are weak' would be a very odd one and have different implications than tired as noted by the humorous comments (Which I love by the way, since I have discovered them, they are a fun part of the site)