Processor peaking in 10.5.20

I am experiencing suddden processor peaks.

I have a really powerful computer and I can be cruising at 40% of DSP in Cubase and wham, out of the blue, the processor slams to max and Cubase stops or sometimes locks up for a while before regaining control. Especially annoying when recording vocals or guitar and the take is ruined.

If I work in Logic with a similar project it just doesn’t happen, it is solid as a rock.
No processor peaks whatsoever.

Has anyone else had a similar experience?