If you set MobileSheets in window mode to be too small so you only left list of sub-menus, app crashes immediately or after you try to select one of sub-menus. I've noticed this while trying MobileSheets on my Lumia 930 (so Win10 Mobile) but it applies also to regular Win 10.
Tablet: Surface Pro 8,
Other: Strich BT-FP2, USB-MIDI connection to Kurzweil Forte 7