After any change to a work item, it will automatically be saved. To prevent unnecessary revisions on a work item, there is a configurable delay of 2.5 seconds after the work item is last changed before the save is attempted.
To configure Work Item Autosave, please navigate to the collection administration page and select "Work Item Autosave."
If you need to temporarily disable autosave, there is now a work item form menu which will enable/disable autosave for the work item being edited.
For bugs please use the issue tracker on the GitHub repo.
For feedback/questions contact me on Twitter: @sferg_msft.