The game Pinball Fantasies has a scolling effect at its opening screen. The effect works, but it causes a window horizontal resolution change that is undesirable. The window should be kept at 320 pixels horizontal resolution because the game uses video mode 13h at this screen.
I have been chatting with Daniel Forsgren, one of the coders of the PC version of Pinball Fantasies, and he told me that they have modified the value of the horizontal_display_end vga register in order to produce the horizontal scrolling effect.
Maybe the dosbox implementation sets the window width based on the value of this vga register. There must be a better way of implementing this to avoid this kind of wrong behaviour.