WordPress fix Widget page and switch between visual/text editor broken in 4.8.3

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Widget page and switch between visual/text editor broken in 4.8.3, by dunshoppin

So, as it says in the title, I can’t do anything on the widgets page, nor switch between the visual and text editor tabs since the automatic upgrade to 4.8.3 on the 31st October. I’ve disabled all plugins and installed Twenty Sixteen, but no improvement. The site normally runs Atahualpa and everything is up to date.

I have other sites running 4.8.3 in the same shared hosting environment and they don’t have the same problem. I’ve fixed it for now by rolling back to 4.8.2 and turning off the automatic updates.

Just for info, I have twice (three times including the first auto update) rolled forward from a working 4.8.2 to 4.8.3 and the problem was repeated.

Any ideas?

Widget page and switch between visual/text editor broken in 4.8.3