Required choice column reverts to previous choice in library

After more testing, we understood the conditions when it happens:
- only Excel files, only when the file is opened in the client application
- all types of columns: choice, text,...
- all browsers, even in private mode
- all sites and libraries
- all users

Steps to achieve the wrong behaviour:
- in a library, change a property of an Excel file
- open the file in the application
- go to File > Information > Show all properties
- the property is not updated in the file

We opened a ticket with Microsoft. Their first recommendation was to synchronize the library. We also realized that the property would update if we waited more than 1 min and refreshed the page before opening the Excel file.

And finally, we found that it was a cache application problem.

To correct the behaviour, in Excel, Open File > Options > Save:

• Click on ‘Delete cached files’
• Check ‘Delete files from the office document cache when they are closed’