gui error after changing video settings

hi folks,

after installing a new skin (amber), i experimented with different settings under video => windowed, full screen

I use a 3monitor solution on a AMD R9 390 which gives me 5760×1080 as a single monitor, and on activating fullscreen on monitor #1 Kodi crashed

Therefore two simple questions:
– is there a command line parameter to start kodi in a default video mode (e.g. 800×600 windowed)?
– i corrected some entries in the guisetting.xml, i deleted it, always crash and the guisetting.xml is overwritten with the last false entries => why is this so?

any hints or links to existing posts are very welcome
regards aplrapid