permission manager will not stay open

Just don't load or unload other plugins while the UI is open.
Should work fine.

Plugins should only reload when you tell them to via console, or less commonly by some timed plugin - Say auto switching from main to purge or something like that.

If some plugin is frequently reloading check your console logs to see what it is.
It may have console output to tell you why.

That'd certainly do it.
Thanks for replying so other people know.