Question Weird cooling problem with Dark Rock Pro 4


Mar 20, 2015
i have recently made a new PC (i9 9900k, 2080ti, z390 aorus master, 64 GB Ram, corsair hx850i psu, be quiet silent wings 3 fans) and i have a weird issue when the pc is stressed. For example when rendering and CPU is used aproximately 60-100% it gets very loud but more importantly its very unstable and the noise keeps constantly getting up and down quickly and randomly even if the temperatures remains almost the same.
I tried turning off GPU fans to see if its not the GPU - it is not. I tried changing all the fans from quiet mode, to normal, to performance to full speed and it also didnt change the behaviour. I tried manual fan curve and also nothing, it keeps happening.
It is also not because of the PSU.
So only possible thing that i can think of is the middle fan of the Dark Rock Pro 4 CPU cooler.
The cooler has two fans but their cables are joined into one cable that leads into the CPU FAN slot on motherboard. So in theory they should be running at the same RPM, because there is no way to control them in bios or in mobo software separartely. But it looks like the middle one (which i cannot see because its in the middle of the cooler) is going on in random speeds. Is there some way to prevent this and control it? The visible front fan on the cooler seems to be working ok and is spinning at speeds that are set for it.
Or could it be something else? It is very loud and because its not constant unchangeable noise but it keeps fluctuating up and down, it is very annoying. Thanks for help.