Zitat von iRacing UI / Member SiteWe are investigating a bug where some drivers are unable to move when starting a Race from the pits. We suggest drivers not start Races from the pits.
I haven't seen any reports that involved oval racing, but yeah.
EDIT: Btw, this apparently goes back to the new build release a few weeks ago. No mention of a recent hotfix or patch breaking it.
Concerning Atlanta, the car is a little more stable on the high side when on cold tyres, and looser when someone following is within half a car length.
I have no idea about the front downforce. I'd imagine clean air on the nose may make the car looser, whereas turbulent air may make it tighter, but inconsistently so.
The tyres will come in after two laps or so, but it's best not to slide the rears.