Error 502 Bad Gateway Openresty while uploading


I encounter the 502 bad gateway error each time I try to upload a file with a form input type file.
It was working well until monday I think. I have uploaded a file perfectly and, 1 minute after, it didn’t work anymore for the next one.
The website works well, only the upload is impacted.
I checked the status of my website, everything seems to be OK (quota, database size).
I tried to desactivate then reactivate FTP, nothing changed.

My website :

Thank you in advance if you have an idea.
Have a nice day.

502 error usually are only temporary - maybe it has resolved now?