Problem Activating Worksheets from Modal Form
In Excel 2016 if a modal user form attempts to activate a protected sheet then it will not activate properly.
This bug was also noted in Excel 2013 and appears to have been fixed in Excel 2016 for unprotected sheets but protected sheets still do not activate properly.
The symptoms of an improperly activated sheet are that entering values will actually cause the value to be entered on the previously activated sheet. If that cell is protected (on the previous sheet) but not protected on the active sheet it will display that the cell is protected. Scrolling with the mouse wheel doesn't work, the cursor can leave the screen eg. using the arrow keys.
Looking at information a workaround is to activate the sheet indirectly using Application.OnTime Now, "ActivateSheetx" however this is far from ideal.