One suggestion---not fancy analysis, but perhaps instructive......simply put your camera on liveview, magnified as much as possible, with the crosshairs centered on a star, and let it rip for a while. What is the motion of the star? North-south drift is bad polar alignment. East-West is what you are looking for.
Here is another experiment you should run.
Decrease your gain, or ISO, or aperture (simply cut a round circle maybe one fourth of your aperture diameter in a piece of cardboard and tape the cardboard to the front of the aperture). Point is, I'm asking you to take a long exposure, and don't want it overexposed.
Polar MISalign your mount. That is, make sure you are ten degrees or more off on polar alignment.
Now take a ten minute exposure, or fifteen if you can without blowing out the background.
What do the stars look like? Are they pinpoint (they should not be with polar misalignment), a continuous streak north-south (this is good tracking with polar misalignment), or are they jerky streaks (this would be some form of bad tracking....) ?
The purpose of polar-MISaligning the mount is to get the stars to move consistently north or south of where they were.
The purpose of exposing a long time is to see if you are getting something periodically. That is, you get it, then you don't get it, then you get it again. You may not be able to tell this in a shot that is not as long as the period of the error. (That short shot may be while the mount is behaving, but the next shot may be when the mount is NOT moving correctly.) You need a longer shot to analyze it all.
If you did not misalign the mount, the movement might be back and forth, retracing pixels that had already been exposed. But with the misalignment, the star has shifted north of south.
I don't know if it will help, but it is worth a try.