One of several bugs in frames since changes were made in ST7.
You will also find if you change the dimensions of the cross-section profile you will probably have to redefine the position again.
It doesn't actually remember the keypoint, just the position of the cross-section origin (0,0,0 ?) relative to the path. So, a 40x40 square centred on 0,0,0 in the cross section sketch but located on one corner in the frame, will be 5mm out of position if you change the section to 50x50.
Another bug I've found that I'm sure wasn't in ST6 frames is when you have to send the section around sloping faces. It doesn't always follow the face correctly.
HP Z420 16GB RAM Quadro K4000 ST10 MP3 on Windows 10 Pro 64.
Please file an incident report with GTAC. This is the only way to really get things fixed. The most efficient moethod of getting this done is create a zip file containing movies, files, and text that fully define the probem and upload them directly to GTAC with the files.
I already have too many going that are more important to me than this.