Mac kernel_task 75% after closing Nuendo


When i reboot my iMac, open Nuendo, everything is ok. Nuendo uses about 60% of one core and kernel_task about 10%

after an hour of work the kernel_task is 75% and remains that even after i close Nuendo.

Nuendo acts sluggish, everything seems to have a certain latency. When you copy audio blocks its very hard to position them and zooming into audio files in the audio editor goes really slow.

I recently moved my orchestra to an external slave PC via network and VEP6 could that be the cause?
although it doesn’t use much % in the Activity Monitor.

Imac 27" 2013 32gb - RME fireface UC -

do you got much programs/tasks on your iMac?