I have a terrifically annoying bug that shows up somewhere between X and GTK and all Gecko-based browsers. While I'm scrolling down in a web page with the mouse

I have a terrifically annoying bug that shows up somewhere between X and GTK and all Gecko-based browsers. While I'm scrolling down in a web page with the mouse wheel, within a few seconds the page will stop moving. The mouse will still move around, but it will stop changing its cursor based on hovered elements, and further mouse actions will do nothing. It will unjam itself something like 30 seconds later if I wait, or immediately if I press any key. Then all the queued mouse events will rush through at once, so if the key I hit was Ctrl, the page's contents zoom out and I have to reset it. If I hit Shift, it walks back through the history and I lose my place. So I was hitting Alt for a while, besides shopping for a distro. I couldn't debug it normally, or even get a clue about which package needs to be downgraded, because I can't pop over to the terminal without unjamming it. So I'd need another machine with which to SSH in, and those are all unusable ATM (well, I probably just needed to suck it up and install SSH on the phone). But ${somehow} I found out that triggering a redraw with ${something} also unjams it, so I set the clock in the XFCE panel (also GTK, FWIW) to display seconds as well. Now it still jams but always for less than a second.