It is tough to show exactly what I mean since the time/iteration and the Parallel -> Timer -> Usage -> "Avereage wall-clock time per iteration" are roughly the same throughout the simulation. However, when I watch the console in real time it is clear that there is a slow down.

"Slowed Down" Speed:

Initial Speed: 

Pause and re-start to me means hitting "stop at the end of time-step" waiting for the simulation to stop and then pressing calculate again. I am sure that we would see the same speed increase by saving the case and data and re-opening another instance of fluent.

I am using 2021/R2. 

I am not sure if this is a linux cache issue as well, have you seen anything similar for Linux HPCs?