WordPress not showing pictures after 5.5 update - "Enable jQuery Migrate Helper" solution doesn't work

Question

I migrated to WP 5.5 and as many, I have issues with pictures not showing.

I tried to apply all the solutions I found on the internet but none worked:

• install "Enable jQuery Migrate Helper"
• disable old plugins
• disable Smush, caches & co.
• I even downgraded the site back to 5.4.1
• ...

The images are still not showing. But it must be linked to the Lazy Load anyway... You can see an example here:https://excel-malin.com/en/excel/test123/

This is the code it shows for the picture. It looks like the browser is still showing the 1 pixel lazy load "fake" picture and don't switch to the real picture.

<img class="alignleft size-full wp-image-6373" src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" data-src="https://excel-malin.com/wp-content/uploads/2020/09/calendrier_2018_test.jpg" alt="" width="631" height="591" data-srcset="https://excel-malin.com/wp-content/uploads/2020/09/calendrier_2018_test.jpg 631w, https://excel-malin.com/wp-content/uploads/2020/09/calendrier_2018_test-300x281.jpg 300w" data-sizes="(max-width: 631px) 100vw, 631px">

Some more observations:

1. It's not a file permission issue: I checked & re-assigned everything (all folders in "Upload" are 755, all files 644)
2. If I try to show the image in the browser directly with it's URL, it's shown correctly
3. When I create new post, if not saved yet and I preview it, the image is there. Once it's published, the picture disappear.

I don't care for the Lazy Load, I can live with or without but I absolutely need to make the pictures visible...

Big thanks for any help!

Answer 1

I could finally find the reason: it was caused by the "WP-Optimize - Clean, Compress, Cache" plugin...

If someone encounters the same issue, check if you have this plugin installed & deactivate it!