Access 2016: Form border width is too narrow .
Sizeable MDI forms in Access 2016 have a single-pixel border that is very hard to grab with the mouse.
The form borders show as a single-pixel whether the form mode is "no border", "dialog", "sizable" or "thin".
One work-around is to make the form a popup form, but if you make every single form in the database popup, you lose the MDI functionality and the ability to have a genuine popup form. When everything is on top then effectively nothing is.
This creates a serious accessibility issue particularly when combined with the fact that MS Access forms and controls don't resize correctly when the Windows text size/DPI is altered.
Please fix this in Access 2016!!
Simon Sheppard commented
Note this issue is in Access 2016, not Office 365