X11 or Wayland?

Try downloading Firefox from Mozilla, run firefox-bin from the folder and see if you have the same issue. https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

I'm using X11, with firefox-bin downloaded from the Mozilla site I have the same problem.

What happens with Firefox in Safe Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode

Same problem in safe mode

Can you show the issue? We cannot help with what we cannot see. If both versions of Firefox are having issues... sounds like the environment is the issue. How about trying Waterfox? Can you run a VM or live usb stick? Do you have the same issue under another user? What are your computer specs?

Operating System: openSUSE Tumbleweed 20230526 KDE Plasma Version: 5.27.5 KDE Frameworks Version: 5.106.0 Qt Version: 5.15.9 Kernel Version: 6.3.2-1-default (64-bit) Graphics Platform: X11 Processors: 16 × AMD Ryzen 7 5825U with Radeon Graphics Memory: 62.1 GiB of RAM Graphics Processor: AMD Radeon Graphics Manufacturer: HP Product Name: HP ProBook 455 15.6 inch G9 Notebook PC

In VM and liveboot it works correctly. In Waterfox and LibreWolf the problem is the same.

Video: https://youtu.be/2xyLofsvVaQ

Operating System: EndeavourOS KDE Plasma Version: 5.27.5 KDE Frameworks Version: 5.106.0 Qt Version: 5.15.9 Kernel Version: 6.3.4-arch1-1 (64-bit) Graphics Platform: X11 Processors: 8 × AMD Ryzen 5 3500U with Radeon Vega Mobile Gfx Memory: 17,5 GiB of RAM Graphics Processor: AMD Radeon Vega 8 Graphics Manufacturer: LENOVO Product Name: 81NB System Version: Lenovo IdeaPad S340-14API

In VM and liveboot it works correctly. In Waterfox and LibreWolf the problem is the same.

That's what I thought. Firefox from your distro and Mozilla have the same issue, then IMHO it's not the browser. Thanks for the video, but I couldn't clearly tell when the issue happened. It looked like it occurred when you saved the full page. Looking at your system specs, we are on the same version of most things and I cannot replicate your issue. From looking at the manual for your laptop, it looks like it can hold more than 1 drive. I would install another the OS (openSUSE) ;-)) or the same again on the 2nd driver (if you have it). I dual boot Win 11 on this laptop.