I have a series of workbooks that each contain about 24 comboboxes, 24 checkboxes and 1 command button. In general they work fine, but periodically, all the controls in a spreadsheet will just stop working. It's almost like it's in developer mode, but they are not. With the one I'm having issues with this morning, the button & checkboxes are completely unselectable, nothing happens at all when I click on them. With the comboboxes, instead of dropping down with the list of options, they become selected as if I was editing them. If I unprotect the worksheet and enter developer mode, they are all selectable and editable.

I have 20 of these workbooks, this seems to happen to one a week. I generally use a saved copy that works to replace the one having problems, but this is a temporary solution and results in data loss. Any ideas on what might be happening, and what I can do to fix it? I'm using Excel 2013, we upgraded to Office 365 back in June, just before I was brought on to this project.

Thanks in advance for any help, this is frustrating!