Post edit page / blocks not working

This plugin was previously working fine, but now it breaks the post editing screens. I can’t see any blocks! Classic Mode (with the Classic Editor plugin) is ok, but not normal/Blocks mode; the Sidebars fields drop to the bottom, above that everything is stretched so much that “preview” is almost to the edge and “update” is offscreen. The only console errors that I see are :

[DOM] Found 2 elements with non-unique id #_wpnonce: (More info: https://goo.gl/9p2vKq) <input type=?”hidden” id=?”_wpnonce” name=?”_wpnonce” value=?”598cc3e7b7″>? <input type=?”hidden” id=?”_wpnonce” name=?”_wpnonce” value=?”4eaa097e73″>?

I have tried disabling plugins and switching to a default theme. Everything is up to date. The site is hosted on Flywheel.