Over the past couple of weeks I've had two users (One Windows 7 Pro, the other Windows 10 Pro, Both with Office 2016 accessing SharePoint on-premise 2016) report an odd problem opening Office documents in SharePoint.
Once these users opens a Word or Excel file from a SharePoint doc library in edit mode, they cannot open any other office document in edit mode until the user's
C:\user\username\appdata\local\microsoft\office\16.0\officefilecache folder is cleared.
If you don't clear the contents of that folder, all Office documents open in read-only. If you clear the CentralTable MDB and all of the FSD and FSF files from that folder they can open one Office document in edit mode then all others (including the document they just opened) will open in read-only mode. Most users are not yet experiencing this issue, my fear is the problem will spread.