Computer Hope

Hi everyone!

I've had my PC for a few years now and I did not have any major issues with it.
Today I noticed a quiet whistling sound that lasts around a second and repeats every 6 or so seconds.

After I took the PC apart, I concluded that the sound is coming from the PSU.

The sound is really quiet, but since I made a quiet build, it's annoying when the PC is under low load or idle.
I recorded the sound and added a visual aid to pinpoint it (on-screen text saying "Now"). Note that the sound is amplified several times over, so everything sounds quite noisy. Also, the ticking sound heard in one of the videos is from my alarm clock, has nothing to do with the whistling sound coming from the PC.

This is my build:
Mobo: MSI B450 Tomahawk Max
CPU: Ryzen 7 5800X3D
GPU: XFX RX 6600
RAM: 16GB DDR4 RAM
Cooler: beQuiet! Dark Power 4 Pro
PSU: Corsair RMx Series RM850x 850W V2
3 Case Fans (not sure what brand, but disconnected all of them and the noise is still there).
4 SSDs (1xSamsung Evo, 2xKingston, 1xAMD). There are no HDDs in this PC.

Here are two videos of the issue I recorded:
https://youtu.be/6ODvKH7OF4g
https://youtu.be/Fp_ULNBFXZY

I already posted on a couple of other forums and got no help.

Any help would be much appreciated.