[wp-trac] [WordPress Trac] #42750: Javascript breaks in some backend pages

[WordPress Trac]

#42750: Javascript breaks in some backend pages
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 Reporter:  viajarapie         |       Owner:
     Type:  defect (bug)       |      Status:  new
 Priority:  normal             |   Milestone:  Awaiting Review
Component:  General            |     Version:  4.9
 Severity:  normal             |  Resolution:
 Keywords:  reporter-feedback  |     Focuses:  javascript
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Comment (by viajarapie):

 @knutsp I deactivated all plugins, cleared the browser cache, then
 reactivated one by one. I tried loading the Post Editor each time. Here is
 the report:

 With all plugins deactivated, I recovered part of the missing
 functionality but not all. The HTML view was still not working. I could
 not add media. On the other hand, the Screen Options and the Help buttons
 were working again. I could assign Tags. When scrolling down, the Add
 Media button and all the edition buttons would stay on top of the page
 (previously they would all scroll up).

 When re-activating plugins, everything stayed as described in the
 paragraph above except for 2 plugins:

 Jetpack
 Media Library Assistant

 Re-activating any of those 2 plugins would mean the Post Editor had all
 the problems described above and the issues that had been corrected
 reappeared: Screen Options and Help buttons didn't work, the Tag
 assignment didn't work either and all the header panels (edition buttons
 et al) would scroll up.

 The browser console would show the same errors described in my reply # 2
 above, even with all plugins deactivated.

 My uninformed summary is there's three suspects:

 Theme
 Jetpack
 Media Library Assistant

 Everything was working well with WP 4.8.3

 Right now, my frontend works well, as far as I've noticed. It's my backend
 that has problems but it's rather serious as I cannot post new content.

 I will consider downgrading WP to 4.8.3 so I can keep working with the
 site. I don't dare to change the Theme as the theme developer told me I
 could miss settings that would be hard work to recover.

 I welcome your help. Hope you can find out what the problem is. Thanks a
 lot for your work!

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Ticket URL: <https://core.trac.wordpress.org/ticket/42750#comment:7>
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