App does not close on exit when cloud sync is enabled

[colanct]

The app (in Windows 10) does not auto close on exit after making changes with sync enabled.
After selecting "Save & Quit", a notification confirms saving, followed by the syncing notification.
But after that, the "You have not saved..." dialog is shown indefinitely.
The sequence repeats every time when re-selecting "Save & Quit".
Closing the "You have not saved..." dialog, followed by the Close app (X), does close the app after the above sequence.
If the app is reopened and then closed without having made any changes, it closes immediately, as expected (presumably as the save & sync is not invoked).

The above behaviour is consistent across two Win10 PCs.