Files saved from Microsoft Office disappear

When I save files from Microsoft Office (e.g. export something from OneNote) into a virtual Cryptomator drive in Windows, they disappear. The files are not in the folder or anywhere else.

Google Drive says it has synchronized everything. Still the files are gone (or better: never have arrived on the virtual drive Z:).

Cryptomator 1.3.4, Windows 10 latest version, MS Office 2013, Google Drive latest version.