That's a fair concern. We don't have extra steps to the interview process, our team votes only on the submitted code. However, We did not spend enough time thinking about automating as many of those steps as possible as we should have.
For some challenges we wrote a public linter and tester, so folks can self-test and iterate before they submit the code:
The good news is, if you've run this process a bunch of times with votes, you should have a lot of raw material from which to make a rubric, and then the only process change you need is "lose the vote, and instead randomly select someone to evaluate the rubric against the submission". Your process will get more efficient and more accurate at the same time, which isn't usually a win you get to have. :)
For some challenges we wrote a public linter and tester, so folks can self-test and iterate before they submit the code:
https://github.com/gravitational/fakeiot
I'll go back and revise these with the team, thanks for the hint.