Hi, just registered to add to this observation. I've been fighting with this rather annoying issue for a long time now, even with the Windows 11 and the latest HWiNFO beta. It seems that when the tray icons have similar labels (tooltips), for ex. "Drive Temperature" and "Drive Temperature 2", no matter what, one of these will not stick, and will hide under the arrow. This is solved by completely renaming one of the icons in the HWiNFO sensor settings.
I confirm changing the sensor names solved the issue for me. (w11 pro+hwinfo 7.26-4800).
Strangely, I also had to go to taskbar corner overflow settings, disable and re-enable each of the icons in order I wanted them to appear.
Now the behavior is consistent across reboots. Thanks!