[wp-trac] [WordPress Trac] #51322: Upgrading from 5.4.2 to 5.5/5.5.1 gives multiple problems

[WordPress Trac]

#51322: Upgrading from 5.4.2 to 5.5/5.5.1 gives multiple problems
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 Reporter:  torqueing           |      Owner:  (none)
     Type:  defect (bug)        |     Status:  new
 Priority:  normal              |  Milestone:  Awaiting Review
Component:  General             |    Version:  5.5
 Severity:  critical            |   Keywords:
  Focuses:  ui, administration  |
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 After upgrading to the 5.5 series of WordPress there are several problems:

 1. the icons from the classic editor disappear and it's impossible to
 switch from text editing and visual editing. There are also problems with
 the Gutenberg editor.
 2. Sub menus don't display when you hover the cursor over them and only
 appear *after* you have clicked on the menu item itself.
 3. The 'select-all' checkbox in the plugins section doesn't select any
 plugins, it just checks its own box

 I have created a couple of cloned website for you to see the difference. I
 have also tested the problem with the WP-Downgrade plugin and the problems
 disappear when downgrading to 5.4.2. Please ask if you need access to the
 back end to test for yourself

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Ticket URL: <https://core.trac.wordpress.org/ticket/51322>
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