synthetic motion confusion
This has been observed in the wip/surface-state-rework branch, but Jonas says he's also reproduced it on master:
Open the hamburger menu in widget-factory. If you get unlucky, hover does not work the first time you do it. According to Jonas' analysis, we're receiving a synthetic motion event on the toplevel while the popover is up, and end up putting the pointer focus location in the toplevel, causing the popover to get starved of events.