I switch our project to version 3.6 of Monogame (OpenGL on Windows) and i found that GraphicsDeviceManager.SynchronizeWithVerticalRetrace does not work anymore.
It works just on Initialization state - there I can set SynchronizeWithVerticalRetrace successfully, but when I am trying switch synchronisation during the game - nothing happened. I am calling GraphicsDeviceManager.ApplyChanges() but it stay unchanged.
In old version 3.5 it works properly.