Memcached - installation problems.

EDIT ON
It looks like my Memchached installation is broken after the Debian update.
So it's not a Emon problem.
EDIT OFF

I'm trying to install Emoncms with Nginx on the latest Debian.
I have two errors that i want to solve before i log in the first time.
I have ExpressionEngine and Zabbix running on this machine without problems...

I already tried to increase the maximum Memcached key/slab size:
https://ma.ttias.be/phps-memcached-sessions-failed-to-write-session-data...
 

2016/02/25 22:16:45 [error] 58149#58149: *1 FastCGI sent in stderr: "PHP message: PHP Warning:  Unknown: Failed to write session data (memcached). Please verify that the current setting of session.save_path is correct (unix:/tmp/memcached.sock) in Unknown on line 0" while reading upstream, client: 192.168.0.150, server: proteus-iv.skulltronics.net, request: "GET /stats/index.php HTTP/2.0", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "proteus-iv.skulltronics.net"

2016/02/25 22:16:47 [error] 58149#58149: *1 FastCGI sent in stderr: "PHP message: PHP Warning:  session_start(): Write of lock failed in /var/www/proteus-iv/stats/Modules/user/user_model.php on line 101

PHP message: PHP Warning:  session_start(): Unable to clear session lock record in /var/www/proteus-iv/stats/Modules/user/user_model.php on line 101" while reading response header from upstream, client: 192.168.0.150, server: proteus-iv.skulltronics.net, request: "GET /stats/index.php HTTP/2.0", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "proteus-iv.skulltronics.net"