excel on ipad files are read-only

I have Office 365 Home on my Windows 7 PC, iPhone 5s and iPad 4. All works fine on PC and iPhone. On iPad Excel files that have any protected cells open and read-only. I cannot edit ANY cells. This is a time sheet spreadsheet with some protected formulas and unprotected data entry cells. When I attempt to select an UNPROTECTED cell the "read-only" message pops up and I cannot edit. Again, this only happens on the iPad. Is this a known bug in Office for the iPad?

Thanks!