CPU Spikes...only after Export Audio, wth reimport into pool

Strange issue I’ve been having for ages, and it’s really beginning to bug me. My system is rock solid normally. Currently using USB2 Focusrite Scarlett 2i4 (must update my sig). No glitches, no spikes and I can throw as much at it as I want in terms of CPU-heavy VST’s etc.

BUT…

As soon as I Export audio, as a wav and reimport into the pool and a track, I get the cpu spikes. I then have to restart Cubase to have it settle again.

Anyone seen anything like this of have any ideas what might be causing it?