Thanks a lot for taking the time to try to reproduce the issue.
I have tested everything you suggested, but unfortunately the problem is still happening.
My current version is:
Opera One 134.0.5954.56
Stable channel
Windows 11 64-bit, fully updated
Chromium 150.0.7871.224
Opera reports that it is fully up to date.
I also disabled:
opera://flags/#hardware-media-key-handling
and restarted Opera, but the issue still occurs exactly the same way.
I have also confirmed that the problem happens both in my normal Opera installation and in a completely clean portable installation, with a fresh profile, no extensions, no imported data and no account signed in.
The issue only happens in Opera. I have tested the same behavior in Edge, Firefox and Chrome on the same PC, and I cannot reproduce it in any of those browsers.
So at this point it seems to be something specific to Opera on my system rather than a general Windows or keyboard issue.
Thanks again for testing it on your side.