Hey Giulio!
I think it’s very likely. I don’t know how exactly “ewww image optimizer” plugin works, but for now WP doesn’t support the WebP yet, and Regenerate Thumbnails uses WordPress core functions.
You can follow this ticket for more details on how it’s going: https://core.trac.ww.wp.xz.cn/ticket/35725
There are some very recent movements there. Hopefully, it’ll have a good support soon! =)
/wp-json/regenerate-thumbnails/v1/regenerate/20978 gives a error 503 with admin role.
Interesting! In this case, the error could be related to something in your server.
Are you able to debug and figure out if it’s running the method RegenerateThumbnails_REST_Controller::regenerate_item (file /regenerate-thumbnails/includes/class-regeneratethumbnails-rest-controller.php)? I suspect the error could be something before that.
mh, there is a output saying: The error is: {message}
Where do you see this output? And could you paste here the “message” too? Or was the message really this The error is: {message}?
Also, if you could check the logs, get the whole request response, send us step by step how to reproduce the issue (maybe you could test with a new jpg and a new webp image trying to find a pattern in the error) and gather as much detail as possible, it would help to find out what is going on. 🙂
I the error is really only: The error is: {message}.
PHP-LOG says: “libgomp: Thread creation failed: Resource temporarily unavailable”
hopes this helps to find the problem.
System is Ubuntu 18.04 with PHP 8.0.5
Since you’re having this error and the request is returning a 503, I’d recommend contacting your server support. It seems some problem happening on the server-side. 😉
I had similar issues today (never before this), and checked debug.log – the server was timing out. Set PHP max_execution_time from 30sec to 120sec and it fixed it.