I'm not sure, honestly. We haven't heard of that issue. What I'd recommend is going to the Joomla Installer -> Manage area. Then, search for "jlinked". Uninstall anything that is JLinked specific, like the JLinked - Authentication, JLinked - Content, JLinked - System or JLinked - User plugins or the JLinked component itself. Those should have been uninstalled already, but hopefully that gets you going.
Keep me posted on what you find.
Thanks,
Alex