This happens from time to time both on firefox and chrome on windows.
After i edit a post multiple times: edit a word, then press ctrl+enter then edit again, it happens sometimes that i cannot scroll with my touchpad/mouse on that topic.
I can scroll with j/k and use keyboard shortcuts but not use the mouse scroll.
Clicking the title of the topic for a go to OP doesn’t fix this, and nor does clicking a second time on the title (for a refresh).
What does help is doing a whole page refresh (eg: click refresh button of my browser, or ctrl+r or ctrl+f5).
No luck so far, but as @TheBestPessimist said it happens “from time to time”, so I’m not counting it out yet. I’ll keep playing with this, and leave this open for a bit in case others can repro it.
Sodenote: since the op of the theme component is not a wiki (so i can’t edit it): can you please add the keyboard shortcut there in the OP, instead of only in the comments?