SP Staging version 4 is now available. 

Because we take seriously users comments, we fully restructured the component. Many of the bugs were caused by functionality that people do not use. Therefore we removed the problematic functionality and we made it much simpler to use.

Now it is as simple as core Joomla! extensions manager with the big difference that it can install/update extensions on many sites at once! Thanks for your review that initiated the process of fixing things.