I usually check the magenta line on the VFR map. For me when I know the STAR isn’t being followed is when the magenta line switches from moving to the next waypoint and instead switches to the last waypoint before the runway. Since that line becomes the magenta line, that’s when the AP tries to follow that instead.
I suggest you make some recording like I do here. It makes it easier for everyone to understand what you experience than just typing all the waypoints in the post, and we still left to “imagine” what’s happening instead of seeing it actually happened through a video recording.
This is a video of mine with a similar thing. Note that as soon as the AP deviates, I opened the VFR map to check where the magenta line is at. And I override the heading mode.