Dock issues

Another path may include troubleshooting the main system by testing

via a new user account. And if nothing else, re-install just the system.

•How to test an issue in another user account on your Mac - Apple Support

•About macOS Recovery - Apple Support

•How to reinstall macOS - Apple Support

•Use safe mode to isolate issues with your Mac - Apple Support

Or as simple as re-start in Safe mode, and after looking about, restart

normally to get back into complete system. ~ Seldom if ever drastic

measures are 'required' to handle the modern macOS or recent OS X.

•How to use Time Machine to back up or restore your Mac - Apple Support

IF you happen to have a backup such as Time Machine, or a full 'system

clone' on external (bootable) storage, that too is a means to resolve this.

After removing the .plists, did you restart the computer?

You need to look in your user Library/Application Support/Dock for the .db. Use the Finder “Go To Folder” command. Enter ~/Library/Application Support/Dock. Move the .db to your desktop.

Then try a dock reset.

Applications/Utilities/Terminal enter the command

killall Dock

Log out/in test. If it works okay, delete the .db from the desktop.

If the Dock is the same, return the .db to where you got them from, overwriting the newer ones.

Thank you for re-stating the 'go-to-folder' path & instruction for this issue.

..Years ago I may have used that twice (in decades of Mac use) & forgot..

And usually avoid terminal, etc ~ while too busy offline to consider non-GUI.