I implemented a fluent theme to my application but when I hit the button to change the light and dark theme my main menu moved. If the light theme is in use then my menu items are moved to left (prefered) but if the dark theme is in use then menu items are moved to the right. Whatever is default I need to have them in the same position in both dark or light themes.
I couldn't reproduce this problem with the latest release and a new app. Can you inspect the panel menu to see where the size setting comes from? Use your browser's developer tools.
Does the problem appear in a new application or when browsing in incognito mode? There is a chance you see an old version of the dark theme.