To reproduce:
* in workspace 1, view a page in epiphany that shows tooltips when you hover the mouse over links (e.g. launchpad).
* hold down the "Win" modifier key (assuming you have workspace switching shortcuts of Win-1, Win-2, etc).
* move the mouse cursor over a link, revealing a tooltip.
* (quickly) press the "2" key to complete the Win-2 keyboard shortcut, switching to workspace 2.
* the tooltip is still displayed, obscuring whatever it is you're trying to look at on workspace 2, and no amount of mouse wiggling or clicking can remove it. You either need to wait for it to disappear of its own accord, or switch back to the original workspace and move the mouse over something that isn't a link.
For some reason, I see this several times a day (probably because I quickly flick through my workspaces looking for a particular window from time to time, and if the mouse cursor happens to be over a link and I'm moving it slightly as I flick past, I trigger this). It's an irritation rather than a major bug, but still irritating.
I would like to confirm this bug and add my request for it to be fixed. I run in to it as well on a daily basis, and it can be a serious annoyance at times, obscuring important regions on screen.