There needs to be at least one checkpoint in the level. Without one, here's what the game's thinking:
Ok, he's in the finish line sector, has he hit all the checkpoints? Yup, give him a lap, and unhit all the checkpoints. What's that? No checkpoints to hit? No matter, just keep going.
One 35th of a second later.
Ok, he's in the finish line sector, has he hit all the checkpoints? Yup, give him a lap, and unhit all the checkpoints. What's that? No checkpoints to hit? No matter, just keep going.
One 35th of a second later.
Ok, he's in the finish line sector, has he hit all the checkpoints? Yup, give him a lap, and unhit all the checkpoints. What's that? No checkpoints to hit? No matter, just keep going.
And keeps doing that until;
Ok, he's in the finish line sector, has he hit all the checkpoints? Yup, give him a lap. What's this? He has all the laps he needs to win? Well end the level then!