I just upgrade to 4.8.3. When I rebooted, the system tray will not stay on the right side of the panel. It moves depending on how much free space is available to the left. Adding a separator does not seem to work.
Edit: Forget it, I found the problem.
Right click on the panel and choose 'Panel' -> 'Panel Preferences'. Then go to 'Items' and add a seperator that you move with the arrows to the desired place. Close that window and do another right click now to the area where the seperator is located, enter the 'Properties' and choose 'Expand'.
edited by Sproggy: please do not link to offsite, put the resolve you used to help with your issue here to make it easier for the other users.