This turned out to be the .toolbar{} with a .bottomBar element. I've replaced it for a custom one and the navigation now works as before (actually I believe that's even smoother). https://mastodon.social/@xmollv/111090753952350763
@phill ^ in case it helps in any way!
@phill I think I had issues on every OS release with it, but so far there's always been a fix. Now I'm just rolling my own (which looks identical to the system one), pretty sure this one won't ever break!