Help /opt/zextrascommon/bin/java - Dfile.encoding ... has to many process and consumes SWAP & Memory

I had a fresh install of carbonio. I am using it since 2 weeks. The server is actively used by 3 person and I allocated 16 GB RAM (I migrated data from Zimbra)

But almost everday the server responds slow and when I checked with htop the process described in the topic consumes memory and it keeps it.

It maxed out SWAP and 11/16GB ram.

What is the problem?