Try resetting the Workspaces:
Reset a workspace
Reset the current workspace to return to its original, saved layout of panels.
1. Do one of the following:
• Click the Workspace menu icon and select Reset to Saved Layout.
• Choose Window > Workspace > Reset to Saved Layout.
from here:
https://helpx.adobe.com/premiere-pro/using/workspaces.html
By @Peru Bob
That never fixes the issue permanent. If it do fix it, it´s only temporary and the issue with panels that "moves around" in the workspace will be back soon again. It should not be necessary to reset the workspace twice a day as a workaround for a bug that gets no attention.
I see this on fresh installs on computers were Premiere Pro has never even been installed, when creating brand new projects. So old workspaces, old preferences, old OS-installs, previous installs of Pr, previous corrupted workspaces can always be ruled out of the equation regarding this. This is simply an issue that comes out of the box with Premiere Pro and it has been like this for years.
Another thing that is an issue is the Icon View v.s List View in the Project panel. The default is Icon View and i do always set it to List View. For some reasons new project often switches back from List View to Icon View for no obvious reason next time one open the project. Some times it don´t... It seem that one need to switch back manually a couple of times before Premiere Pro "understand" that List View should stick.
It seems that changes made by end users don´t stick for some reason.
I appreciate your help though! 🙂