@Maijestro the case is huge and certainly not narrow
https://www.coolermaster.com/en-global/products/mastercase-sl600m/There is a lot of airflow in there (2x 200mm fans in the bottom) and I can feel the cold air coming out the top as it is a vertical cooling case aka "chimney effect". I just increased the fans to Medium. The noise is bearable and the temp is now 65C, but I agree with this much airflow it should be cooler.
I am tempted to remove the heatsink from the CPU and replace whatever thermal solution is there, paste or adhesive but knowing my luck I'll make it worse so I'm reluctant to do that.
Maybe something is keeping the CPU at high load? I don't have a CPU meter running so I don't know. That's the thing, it might be hot at idle, but it doesn't get much hotter under full load so if I had to guess, I'd say something here isn't right.
[EDIT] No - 0% according to CPU Dockey