Arun,

Alt/Az position may appear to change slightly because it gets calculated from these polled values from the mount: RA, Dec, and Local Sidereal Time.

Although Dec is constant when parked, RA and Local Sidereal Time change so that makes the Alt/Az position appear to move around.

As to why the mount doesn't seem to park, we would have to see your log(s).

Specifically:

1) Connect to your mount.
2) Slew the mount somewhere away from the park position
3) Park the mount.
4) Wait at least 10 minutes after the park, then disconnect from the mount.
5) Use the AP driver's Log Zipper utility to zip your logs and settings files.
6) Email the zip file to me at groups3 @ gralak dot com.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver