Steps to reproduce:

1. Open chrome developer tools -> Network -> Slow 3G
2. Edit dashboard
3. Make some changes in widget and save widget
4. Save dashboard
5. Wait until dashboard reloaded
6. Check changes in widget

Result:
Widget changes not saved. After saving widget, the dashboard button "Save changes" is enabled, after a few seconds it becomes disabled and then enabled again. With slow internet enough time to save the dashboard before the button become disabled
Expected:
The dashboard button "Save changes" immediately disabled after applying any changes in widget

In 4.0 version seems to work fine.