We have had the same issue several times with AP.
Yesterday we adjusted our follow distance from 4 to 5 then 6, MY still wants to rush into a line of halted traffic, or speed up into a turn and then wait until the last moment to brake. Reminds me of how I used to drive as a teen. Wasting all of that safety space in front of you while relying on the brakes to save the day. And this with the setting of "Early" on the AP. Wife had several scares, which means the software is NOT up to snuff yet even with the recent update to 18.3.
One thing for sure, AP and TACC are not yet ready for real world driving near multi lane, multi sharp turn, or even easy construction zones. Helps to explain why we see crashed up Tesla's at the SC routinely... drivers who think FSD or AP are really going to do what you do.
Our testing was done one a single lane hills and turns road in the east section of Middletown / Locust NJ shore area... see Navesink River Road, Red Bank NJ on your maps for reference. Super road for testing any sports car, FYI.
Another for thing sure, we love our MY! Those still waiting here, keep on your SC and get a vin. 9 weeks or so average order date to vin, see the Super MY Spreadsheet and keep it up to date.