Images wont upload with new Big Images fiunctionality

[shamai]

With version 5.3 came a new ability to create a big optimized image if the client uploads a very large image. This sort of replaces the full image, although it seems to retain the original image on the server. (not sure why but thats another issue...?)

Seen here:
​https://make.wordpress.org/core/2019/10/09/introducing-handling-of-big-images-in-wordpress-5-3/

Unfortunately there seems to be some bugs. Clients can no longer upload files. They get an error:

"Post-processing of the image failed. If this is a photo or a large image, please scale it down to 2500 pixels and upload it again."

The images uploaded are over 2500, but under 2MB.
I tried setting this new functionality to false using the hook I keep finding online:

add_filter( 'big_image_size_threshold', '__return_false' );

This did not work. I tried returning a new size over 2500 and it still wont work. Is this a bug or am I and everyone on the internet using this hook wrong?

Thank you.

[shamai]

​https://wordpress.org/support/topic/big-image-threshold/

Others having same issue

[lumpysimon]

A client has just reported this issue to me on a site where they had no problems uploading before upgrading to 5.3. Weirdly the error message says 2500px, when I believe the threshold is 2560px.

[fattony4]

I have this problem, too, on my private server (Debian 10, nginx, PHP 7.4, newest WordPress 5.4). If you tell me how to collect the relevant logs, I can provide them!

I found the problem in the nginx error logs (/var/log/nginx/error.log):

2020/04/23 17:40:55 [error] 15290#15290: *77 client intended to send too large body: 65686808 bytes, ...

The solution was to add this line to my nginx config file:

client_max_body_size 20M;

How silly of me to assume it was someone else's fault. XD