I was struggling with this issue for quite some time: leaving the PC on overnight to find it frozen/unresponsive the next morning (I had to use the reset button in order to restart the PC).
It happened few times during normal, daily use, but it was freezing almost every night (from time to time Tixati would throw config errors when starting the next morning after reset).
I couldn't find anything in the Windows' Events log.
The HDD that I'm using for Downloads had some S.M.A.R.T. errors, so I swap it with a brand new one - no change.
I thought maybe it's because of the XMP profile (2800 MHz) so I decreased the RAM frequency to 2400 - no change.
I found it by a chance: my in-game ping was increasing sometimes so I was shutting down Tixati as a part of the troubleshooting process (forgetting to start it again until I needed to download torrent). At some point, I realize there were no freezes when Tixati wasn't running. Tested a bit more to ensure it wasn't a coincidence and yeah it wasn't, no Tixati running - no freezes.

Any ideas on how can I find out why this is happening?

BR,
Petar

Something's weird in your story: you mention your computer is freezing, and also mention that your in-game ping suffers from Bufferbloat (https://www.bufferbloat.net/  ). And you also mention fiddling with frequency settings (overclocking?). Overclocking is a risky process that could cause your computer to malfunction; if you've done that, it's recommended to restore the settings to default, at least for testing. You could also do a stress test; on Windows, try OCCT or Furmark. Bufferbloat is a common issue that may suffice when using BitTorrent programs like Tixati, but it cannot cause your computer to freeze. When your computer freezes, is it locking up completely or still responsive? When it freezes, does pressing the NumLock/CapsLock key on the keyboard toggle the NumLock/CapsLock indicator light? (If it does, it means the Windows kernel is responsive while the rest of the system (the userspace) is locked up.) Is there hard disk activity? Does sound freezes, or gets stuck in an endless loop (which again indicates that the kernel is responsive)? Does your computer also crash afterwards? Is there a delay between when it freezes and when it crashes? When it crashes, does it immediately lose power or show the Blue Screen of Death? Have you tried to check for warnings and errors in the "System" log in the Windows Event Viewer?
Hope this would guide you.