CKEditor 5 Not Saving Changes, Can't Access Source

This may be a Javascript error (the fact that the source button doesn't work may be an indication of this). Can you check the browser's console after opening the edit form and after clicking Source, to see if there are any errors there?

I'm experiencing the exact same issue. I have no idea what's causing the CKEditor to fail but my developper console is full of the same error messages that Chrys reported.

Essentially the changes no longer save and the "source" button no longer works. 

• The CKEditor instance could not be initialized.
• CKEditorError: Cannot read properties of undefined (reading 'toString')
  Read more: https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#erro... read properties of undefined (reading 'toString')
     at _getResizedWidthHeight (js_HJeu4Otun4Y7IKkBjyXAShwISMO_5UTP6QMQVNIYIo8.js:461:24)
     at oo.converter (js_HJeu4Otun4Y7IKkBjyXAShwISMO_5UTP6QMQVNIYIo8.js:650:37)
     at oo.fire (ckeditor5-dll.js?v=1.31.0:5:775753)
     at oo._testAndFire (ckeditor5-dll.js?v=1.31.0:5:362895)
     at oo._testAndFireAddAttributes (ckeditor5-dll.js?v=1.31.0:5:363108)
     at Object.convertAttributes (ckeditor5-dll.js?v=1.31.0:5:363414)
     at oo.<anonymous> (ckeditor5-dll.js?v=1.31.0:5:393309)
     at oo.fire (ckeditor5-dll.js?v=1.31.0:5:775753)
     at oo._testAndFire (ckeditor5-dll.js?v=1.31.0:5:362895)
     at oo._convertInsert (ckeditor5-dll.js?v=1.31.0:5:360988)

I note from https://github.com/backdrop/backdrop-issues/issues/6904 that "DLL builds are sunsetting", which makes me wonder if there's a correlation there.

On top of that I'm having issues with the tarteaucitron library which means the GDPR Cookies module no longer works. It's giving me a 403 ERR_ABORTED error however the init_tarteaucitron doesn't display a permissions error but obviously since it relies on the main library it doesn't work either. I mention it here because both seem to be JavaScript errors so there's a chance they may be related somehow.

• GET https://www.mysite.tld/modules/contrib/gdpr_cookies/libraries/tarteaucit... net::ERR_ABORTED 403 (Forbidden)
• init_tarteaucitron.js?v=1.20.2:1  Uncaught ReferenceError: tarteaucitron is not defined    at init_tarteaucitron.js?v=1.20.2:1:1

I note that the latest Backdrop core update included an update to the CKEditor so something there must have triggered an error. 

@chrys I'm curious if the image you were having an issue with contained a space in its name. I know it was over 6 months ago now so you might not remember but for my issue, the only thing I can think of that an HTML validator points out is the fact that I have a lot of links to documents which have a lot of spaces in their file name. 

This wasn't an issue with TinyMCE when the site was running Drupal but it seems CKEditor 5 doesn't like that for whatever reason.

Unless there's a magic settings tweak somewhere which would help?

I mean, yes it is a JavaScript error, see the error message in my post from 05 August above. And believe me, I've cleared my caches so often, they were squeaky clean

The problem is, it's only affecting one page. Other pages on the website work fine as far as I can tell (at least there's no JS error in the browser console). The problem is, I've reviewed the source code for that page and cannot see any empty src, href, alt or any other html tag attribute. All tags are closed properly and the code passes html validation so I'm confused as per what is causing the error now.

Now since CKEditor is embedded in Backdrop core now, I'm not sure how it would have gotten corrupted in the first place and if I replace it with the source from CKEditor directly, who's to say it won't get overridden again on the next Backdrop update?

jeanloup_sasa, it looks like the error is not happening in CKEditor itself, but in JS function _getResizedWidthHeight(), which is part of the backdrop-image.js file, a CKE plugin provided by Backdrop to deal with image resizing. That function in the plugin was modified 2 years ago.

This leads me to believe that your problem is not Javascript, but the actual body field you are trying to modify. The problem seems to be related with either null, undefined, or faulty value for either height, width, or the parameter resizeWidth that the function receives.

It's impossible to know which of the 3 parameters is fault, since the error you pasted did not contain a line number for the originating error (only for the rest of the call stack).

My suggestion to you is for you to get the HTML code for the Body field directly, and inspect if there is an issue with an image width or height.  You can do that by enabling Devel, and running something like the following:

dpm(node_load(NID));

Replace NID by the node ID of the problematic content. Then find the "body" field and expand it to show its content. Copy and paste here if you wish.

If the page is public, it would be helpful for you to post the full URL so I can take a look and check if I see a malformed image tag somewhere. 

Ultimately, you may need to recreate that page from scratch. This may be a bug, but from your information it's unclear where or why it's happening.

You can try deleting any images in the page one by one, saving the node, and reopening to find the faulty image.