alphatriumph

I have also been getting this error, and have had to convert my own (mis)usage of localize to the recommend function.

I am having the same issue on 3.3.2.

[Accidentally double-posted my comment, please ignore]

This issue appears on all our sites, with all other plugins disabled and on the Twentytwenty theme. It began when we upgraded from WP 4.x to 5.x.

It seems like the plugin needs an update to account for this, or perhaps WP 5.x makes finding out the initiator of a logout event harder/impossible.

Yep, this plugin now completely breaks basic WP functionality. Please rethink your usage of ob_flush (I don’t think it should be necessary) and update.