I implemented my custom webdav server using the python package wsgidav to connect with a private cloud file storage but I'm having problems saving excel files.
When I open an excel file it's in "Protected view" and when I press "Enable edition" the file open again for edition.
But when I want to save the file excel says this:

but there aren't changes from another user because I'm the only one.
I think that the issue is related with this, WebDAV - Microsoft Excel 2016 not able to save back changes , but I don't know how to solve it.
Thanks!
This can happen in Excel if the etag changes after clicking to edit - because some systems generate fresh etags everytime a GET is issued this can occur - use Fiddler to find out whether the etag is staying consistent.