I just discovered a bug related to the resolution of the game window.
If I set the resolution to (e.g. 640x480) using the PreferredBackBuffer (Width and Height), when I run the game, the change is not made (it still has the default MonoGame resolution (800x600)).
But if you switch to fullscreen mode, the indicated resolution (640x480) is applied and when you return to window mode, it is displayed with the defined resolution.
The strange thing is that internally the resolution before and after switching to fullscreen mode is always the same (in our example 640x480px). It should be noted that this bug happens with any resolution other than the default, either lower or higher than the default.
The version that I use of MonoGame is the DesktopGL 220.127.116.111
Link to program with the bug: https://github.com/davidgd72k/TryingResolution
If you have any questions about this, I will be happy to answer them.