I was on a private server last night practicing for an upcoming DTM event at Hockenheim and I left the circuit with 4 wheels once in the penultimate corner (at the exit of T12). I got the usual warning stating my lap will not count, however, when I started the next flying lap, I got no timing graphics and when I crossed the finish line next time it showed an another warning with no text / empty body.
Because you can line yourself up to have a faster laptime by going wide in the last corner and coming out of with with a higher speed than if you don't go outside track.
As @majuh said, this comes with the last patch as you can read here: - Game now invalidates both current and next laps in qualifying sessions, leaderboards and competitions if the player goes off track or wall rides in the last corners of a track. (https://forum.sector3studios.com/index.php?threads/01-06-2017-raceroom-has-been-updated.8196/) I report in our bug tracker, that the warning box is empty after starting a new valid lap.