[ideaoverload]

>Why does this happen even when the instance isn't using all of its CPU?

Probably hypervisor does not assign CPU every time it is requested but it still manages to assign as much as needed because in the end there is some idle time left.

[JulianWasTaken]

We've seen for example, if we have 5 instances running the same app, one instance potentially uses 20% more CPU with tons of CPU steal time, but none are using 100%, the "normal" ones use ~40% and the one with tons of steal time spikes between 60% - 70%.

But rebuilding the instance brings them all in line.