A bad sample from the VSTO team (Microsoft)
Microsoft Office add-in developers are aware of the setting for displaying ribbon UI errors. So, I keep it set everywhere to prevent releasing the code that may lead to UI errors on end users machines. Here is where you can find the option for enabling that: See How to: Show Add-in User Interface Errors for more information. And recently after latest updates for Microsoft Office, I suddenly started getting annoying error message boxes in Excel with UI errors. I have got Excel with the following build numbers installed on my machine: Microsoft Excel 2016 - 16.0.9330.2073 - 32-bit Here is how it looks like in Excel, the error message bombs users twice when they try to open the File menu (the File backstage tab) and go back, or just open another workbook - a lot of cases: As you see on the screenshot, the caption says that an error message is caused by the VSTO design-time adapter for Excel. Then I checked the list of COM add-ins in Excel and found a problematic