I have a session at 125bpm and an audio event positioned at a bar line(bar 10).
The track is on music time base, when I change tempo the part moves correctly and is stuck to the Bar using its Snap point.
Now, if I go into the editor and change the Snap point to a deferent location in the clip and change tempo, the clip dos not stick to the grid and is offset a bit every time I change the tempo.
As far as I understand your description, it is not snapping other way, then expected. Cubase is snapping to the Snap point (not to the Audio Event Start anymore), when you move the Snap point out of the Audio Event Start.
Could you attach a screenshot to be able to confirm, please?