Just now found this while searching for possible causes for the problems @Xlaits is reporting. I wanted to add some info here in case others have ideas.
TypeError: OctoPrint.browser.logout(...).done(...).error is not a function[Learn More] packed_core.js:2406:18
There are some Octolapse errors too, but they are caused by an ajax request that's being blocked (403 in the load settings routine).
Edit: Accidentally posted early. Adding more.
I think the only way to get to the bottom of this would be to disable all plugins but Octolapse and start looking into issues one at a time. Preferably OP could try a fresh install (who knows what those attackers could be doing) and only add Octolapse. I strongly suspect this would solve all of these problems.
Also, @Xlaits, what do you mean by 'twin instances' exactly?