Just two quick comments:
If you have perfect PA that does not mean that automatically your main camera will be centered on the NCP. Errors in home position and things like cone error can easily put you off. Those errors don't matter for the PA process, PA itself is correct. So I would not call it a substantial error per se.
The other thing is that the poles are singular points in RA, and even tiny remaining errors in PA can lead to huge offsets. I strongly recommend to not use any plate solve close to the pole to sync your mount. Just go to some place further away from the pole to do a sync.

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