Real time peaks

i9 7980EX 18 core
Audio interface: RME UFX.
Cubase 9.5.21/ 9.5.30
OS High Sierra

Some drastic real time peaks occure on heavy projects (which takes upto 50 gig memory) with many orchestral sample-based instruments such as Ease West and Kontakt.
After I disabled all the insert plugins, the cpu has reached about 40% but there were many breaks and dropouts as the real time peak sporadically reaches the maximum. Each dropout interrupts the sound so it’s very hard to work in a fluent manner. (Buffer size is normally on 2048 but other attempts from 128 to 1024 didn’t help)
I hope Steinberg can do something about it.
I will have to split my projects with Vienna but I was certain that 40% CPU should not be a problem. There must be a technical issue to fix.

May that be related to Cubase maximum core utilization?
Is Cubale capable of working properly with 18 cores?

Thanks everybody!