@Richard ************
It's not an overstay. You wouldn't be. 90 days report is not your extension.
If you don't do 90 days report, you would be just fined for "not reporting 90days".
The online system is not working well for everyone every time. Your responsibility is you do 90 days report somehow. You do it within the window I described.
How you want to do it is your decision.