firefox does not detect mousemove events

I have an issue, which I saw only on Firefox : after some time (or some event which I haven't identified yet), Firefox does not react to my mouse movement events

meaning :

  * when hovering over an HTML item, it does not highlight/change appearance even if it is supposed to do so,
  * when hovering over a clickable item, the cursor does not change,
  * when hovering over selectable text, the cursor does not change,
  * tooltips do not appear,
  * etc ...

if I trigger other GUI events (if I *click*, or if I *press any keyboard key* -- `[A]`, `[Shift]`, `[Ctrl]` ...), then the GUI reacts (cursor changes, tooltips appear, animations get triggered ...), a bit as if, by handling that other event, firefox realized "oh, the cursor is actually there", but with no external event, my mousenter/mouseleave events seem to be ignored, or stalled.

Running Ubuntu 22.10 (kinetic), and regular firefox snap install (my current version: 109.0.1-1).

As said in the previous sentence: firefox is installed through snap (which, if I am correct, is the default way to install firefox on a Ubuntu system these days) not through an apt package.

Is this a known issue ?