Still issues with max file upload size after following instructions

Hi people,
I’m trying to upload a 3,4G file to my nextcloud. The Nextcloud runs in docker with nextcloud:25.0.6 apache and mariadb:10.5. images. In front of it is an nginx proxy.
I have added client_max_body_size 8G; in the nginx conf for this website. I got confirmation this works, after the error messages about to small client_max_body_size disappeared from nginx error.log.
I also added PHP_MEMORY_LIMIT=8192M and PHP_UPLOAD_LIMIT=8192M to the docker-compose env variables. I confirmed this in the webgui where it shows 8GB max upload limit: . - Album on Imgur

However, I still get an 413 error message when trying to upload the file from the ios app.
And logs in nextcloud container show this (weirdly a 400 error):

   XXX.XXX.XXX.XXX- <username> [08/Jul/2023:12:04:42 +0000] "PUT /remote.php/dav/files/<username>/Photos/ HTTP/1.0" 400 1393 "-" "Mozilla/5.0 (iOS) Nextcloud-iOS     /4.8.5"                                                                                                                                                                               

Any idea, what I’m missing?
Cheers and thanks!