I joined server right after race started (after green light, but before cars crossing finish line).
As soon as car cross finish line (few seconds after start) their lap is increased. But after race finish it stay the same

EDIT: I was localy reproducing this bug, and it seems like it doesnt happen always as described before. Right timing is very important. For example on my laptop I click join to host button when 3rd red light appear on server. Reproduced it in 7/7 cases.