Multi-stage interview processes like this are calibrated that you simply must pass every step of them to do the job. There's no fluff, there's no duplication; each module tests a specific component that the company feels is necessary. If you can't deliver on one component, then you aren't qualified. Harsh, but if you wanted to include an allowance for failing one module, you'd have to add even more modules and duplicate content in them so that you could still feel confident they could do the job. A false positive in the interview process is immensely painful for everyone involved and every effort should be made to prevent that.