There is an issue in the PC version of the game where Daytona and Indy tracks do not render properly after having ran multiple laps.
This happens on Daytona after ~50 laps and on Indy after ~15-20 laps. In both cases this is after a clean start of the game.
At first it is just a missing texture in the background, a section of fence or the crowd but it continues to get progressively worse if you continue to play up to the point to where the track itself does not render in places. This has been an issue since release on the PC version and the only mention of it under known issues suggests turning down the graphics but that does not help at all with this issue. It does not matter if the game is in full screen or windowed mode, the graphics settings can be set very low or very high and the issue still happens at the same point in the same way and does so on different hardware setups. This does not happen on the Xbox version of the game as I have tested both to a great extent.
AI cars in freeplay will in some cases have more HP than the division allows, in some cases a lot more and as a result will attain speeds that are not possible within the division in some cases beating the top leaderboard time by a fairly large margin. I think this happens on both version but I have primarily saw it on the PC version of the game. HyperCars on Homestead Oval are one instance where this happens a lot and I think also on Daytona. I have also saw it in Sport GT class in some cases AI cars having 300 or more HP over the limit for the division.
Both the PC version and the XBox version will sometimes hang and crash when selecting rims for your car. On the PC version [This is the one I play the most] I have saw this several times the game will freeze and after about a minute will return to the desktop. On the Xbox version I have saw it once last night where it froze then after a minute or so shut down my Xbox.
On the PC version after one of the latest patches I have noticed that it I run several races at some point the game starts to stutter a little at first then horribly to the point of unplayability a restart of the game clears the problem and all is well until a number of races have been completed. I have not paid enough attention to this to know for sure how many races it takes. It seems like it is at least 10 across multiple tracks but I have saw this on several occasions when running short races in career mode.
Another issue I noticed is with Lemans. If I start a freeplay race on Lemans the first race goes off without a hitch but if after the race is over I hit restart to run it again I get stuttering and if I try a 3rd time it is very bad. I saw no issues when running the endurance race on Lemans but every time I have tried to run 2 or 3 races in a row without restarting the game I see this issue. As far as I know this happens only on the PC version but I have not tested it on the XBox to confirm as of yet.
On another note it would be nice if we had an option in freeplay to just run a single track rather than having it always try to switch tracks at the end of the race. Would also be nice if there were an option to create our own track list for freeplay and/or multiplayer sessions.