If saving is taking a long time—for example, because the project is large or the network connection is slow—multiple saves can get queued up, and it appears that Easel can erroneously report that the changes are saved even while there are more saves pending. [Update: this has been fixed.]
Additionally, when saves get queued up, it appears that in some cases the “outdated” saves are not completed until all the saves have gone through. This is because of a recent change to prevent conflicts when people inadvertently open & work on the same project in multiple tabs or windows.
I’m sorry for the frustrations this has caused!
We should have a fix for this by early next week. [Update: It’s been fixed, and the following workaround is no longer necessary.]
In the meantime for those who’ve been running into this problem, before you close Easel, you could open the project in a new browser window. If the new window has an empty or outdated version of the project, wait a little bit and reload it. If it’s up to date, then it should be safe to close. (Caveat: Make sure you don’t make any changes in the second window if the saves from the first window haven’t caught up.)