I started a custom championship with the ADAC GT Masters 2015 rule preset, GT Masters 2015 cars and the GT Masters 2017 tracks. In my first 20 minutes race at Oschersleben I noticed two problems: I activated the additional lap in the settings, but it's not working. The race is over after 20 minutes. It's also reproducible in single events. The pit window was open between minute 10 and minute 13, which is pretty short. The first AI cars already came into the pits in minute 8 for their driver change, which consequently didn't count, so they had to pit again.
I have a similar issue with the DTM Championchip. I didn´t activate the extra lap at the end of a race but it´s active in the Championchip (...minutes + 1 Lap).
Hello! When you select a preset some rules are baked into it. For ADAC you can't have an additional lap for example. The bug is that you can still change stuff, which is an issue.