Their recruiters spammed me many times to apply. When I finally decided to apply, we started with a recruiter talk, and then they sent me directly to a Byteboard without any further discussion.

The coding portion requires coding as if it were production code, which means you should include unit tests and a decent amount of documentation. Because of this extra work, there may be a few functions that you cannot yet implement. They probably expected you to implement everything without tests. This would explain why their product goes down so often.

If this process describes the quality of their engineers, I prefer not to use their product anymore.

Review a design document about measuring devices in a factory.

Then implement 5 of the methods.