Multiplayer races finishing early

I'm trying to do a timed race but the race always finishes after 3 laps even if the GDB is set to say.. 800 laps and 15 minutes. The 15 minute timer works but whoever is in first position gets the chequered flag after 3 laps. We have the same track GDB and both have race distance set to time.

Using the lobby

Any ideas?