Not using 100% on smoke simulation ?

Hello,

I’ve recently got a new PC and I’m working on a project with smoke simulation.
The thing is that sometimes the bake takes a short time to finish but most of the time it takes longer.
Task manager shows that the CPU is under 50% usage for no apparent reason.

I read online that high temperatures might underclock and checked with coretemp but that’s not it.
I also set it to high priority which got the CPU from 25-30% to 40%.
I installed the latest drivers.

Did someone come across this issue or knows a fix for this ?
Any help would be greatly appreciated.