Their hoovercraft is full of eels
This is all speculation (conspiracy theory almost) as I have never seen desing of USCIS system. However, it matches general design of such applications. Also it may explain some status updates missing, etc.
USCIS uses some sort of big mainframe system to actually work on the cases (if you look closely at their screens on border crossings, you can see their mainframe-ish applications with green text and old forms -- that is if you can see something through these privacy screen filters ;-). Some time ago they even had mainframe terminals or the like on borders (two Enters on keyboard etc.)
The web app is not directly connected to this system -- if it is then it is really ill-designed and should not work at all. I'm guessing it has its own little database that contains some data only without names/addresses/etc -- both for security and performance.
Now, if a case gets updated in the big system, there should be process in place that would upload this record to the web system. If it fails in certain ways, you will never see this update coming through!
IMHO, they should load the entire database once a week or so to resolve such problems but this process may have its bugs as well, hence some case updates never make it to the web piece.
Most likely, the message you are getting is a result of the small DB down. Once a friendly admin presses the little reset button on that PII Windows box it all runs on, it will come back to normal
Also, not quite difficult to notice, their app is full of bugs. Disable javascript and try to login to your portfolio without selecting customer type - two weeks ago nice crash, not sure now. Etc. Etc.