So, let me clear everything at the start:
- I'm not on shared hosting.
- PHP upload limit is already set for 700mb.
- PHP memory limit is set a 512mb.
- Nginx, PHP-FPM and WordPress' logs tells me nothing about uploads at the time of uploads.
- Restarting the server won't help.
- Core WordPress has seen no updates, and plugin stayed the same. Thing changed there.
- I do use a plugin to send files to S3, but deactivating it so the files stays on the local disk (which as plenty of space), I still get the HTTP error.
We've been uploading 100+mb files perfectly fine for ages. But this morning, trying to upload files that are more than ~5.5mb, I get the HTTP errors. If logs don't throw any errors, what is the else to do to debug those pesky HTTP error on file uploads?