I'm curious as to which server is actually sending this, as I've always had the extras mapped back to 4 and 5 instead, and I think they'd actually be dropped by input-leap. Out-of-range buttons should definitely be dropped here as well, but I'll do that in another commit and merge this, as -- while looking a bit weird to repeat the buttons in the default map -- it solves a problem, and can't really create one for anyone else.

Thank you for this and your other recent PR, by the way.

I'm using https://github.com/pwr-Solaar/Solaar for Logi mouse, but I think the key map is default for the side buttons.

Yes, the issue is actually introduced by the out-of-range buttons which were mapped to strange keycodes. So I also wonder whether more mouse buttons should be supported.

Thank you for your wonderful work and passion!