Hi @Markku_Huusko,
So we can better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
How long had things been working previously? Had all of your content imported?
Do you have any USB devices connected to the Core machine and, if you disconnect them, is there any change?