Mysql Query Cache - Cannot create new user or database

Dear CWP forum users,

Hopefully someone recognizes my problem.
I'm running a Centos7 server with CWP and a high traffic web-shop.

To optimize the server I tried to activate query cache on the database server.

Added the following option:
query_cache_type = 1

After checking the query cache is working. And reduces server load.

Now my difficulty... After activating the query cache, I cannot create a new database and user with CWP.
CWP just working normal and saying the database and user is created.
But in fact the database and user don't exist on the server.

Someone recognizes this? Or knows a solution for this or to debug this?

Thank you very much!! 

No ideas?