Hello Lorenzo,
thank you very much for reporting your problem. We have tried it on several devices and did not manage to reproduce it even once.
I discussed it with developers and Safe clean should not be able to be performed in different way from widget or from the app.
We suppose from your report that the steps to reproduce are like this:
1. you need to be sure you have some amount of thumbnails - to verify it - turn off all Safe clean items in settings except Thumbnails, press back and on Safe clean button there is some non-zero value
2. uncheck Thumbnails item in settings
3. go outside the app, press the widget and return back to app
4. go to settings turn Thumbnails on, press back and you should see that non-zero value from step 1. - in your case that number was zero, right?
As the deletion of thumbnails makes no harm, could you please try again following these steps? Please let us know if you managed to reproduce that widget malfunction. Also would be good if you send us more information about version of Android, version of Cleanup and your device.
Thanks!
