Connection lost on uploading bigger files (Browser)


I`m testing my nextcloud again uploading bigger files < 1GB. Whenever I upload bigger files (>1GB) it failes with error “server connection lost”. No further error message at nginx, mysql or php or nextcloud itself.

I´ve increased my php & nginx & mysql settings for uploading bigger files (max 16GB).

Uploading of files with 200MB doesn´t fail and I see .part files at files storage folder when upload is running. If I upload my 2GB I don´t see any .part files and no php session temp files.

I´m running nextcloud on Debian 8 with nginx 1.10, MariaDB 10.1 and php7.

This is my php pool setting:
listen = /var/run/php/php7.0-fpm-cloud.sock
listen.allowed_clients =

user = cloud
group = cloud
listen.mode = 0660
listen.owner = cloud = www-data

pm = dynamic
pm.max_children = 15
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 7

chdir = /

php_admin_value[open_basedir] = /var/kunden/cloud:/usr/share/php:/tmp:/var/tmp:/dev/urandom:/proc/meminfo:/usr/local/bin:/usr/bin:/bin
php_admin_value[disable_functions] = dl,passthru,shell_exec,system,popen,show_source
php_admin_value[memory_limit] = 512M
php_admin_value[upload_max_filesize] = 16G
php_admin_value[post_max_size] = 16G
php_admin_value[max_input_time] = 76000
php_admin_value[max_execution_time] = 76000
php_admin_value[upload_tmp_dir] = /var/kunden/cloud/tmp
php_admin_value[always_populate_raw_post_data] = -1
php_admin_value[error_log] = /var/log/nginx/cloud.php_error_log

env[PATH] = /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
env[TMP] = /var/kunden/cloud/tmp
env[TMPDIR] = /var/kunden/cloud/tmp
env[TEMP] = /var/kunden/cloud/tmp

My nginx block is the same as the example config at nextcloud docs with having client_max_body_size set to 16G. Furthermore I´ve set a high wait_timeout and max_allowed_package at Mysql to 16G.

And don´t know how to debug further? Has anyone hints?