I think this issue is somewhat different: The UI always immediately reacts on input (e.g. clicking on a menu button), but it doesn't always update the window contents.

Immediately works:
* buttons causing popup/popover menus to open (sandwich menu, downloads menu, bookmarks button…)
* dialog or window controls e.g. profile manager
* Profile manager: selecting a profile from the list by double click
* everything inside popups/popver menus, e.g. inside bookmarks/downloads/sandwich menu

Don't work immediately but have a delay of ~5 seconds:
* scrolling
* opening, closing, switching tabs (note that the window title changes immediately though)
* clicking links
* Profile Manager: selecting a profile from the list by single click
* opening developer console by Ctrl+Shift+I
* showing/hiding menu by pressing Alt

In short it seems like everything in GUI element MozContainer will be repainted after a huge delay. Everything outside (e.g. popovers in subsurfaces, header bar, …) is painted immediately.

Also, when moving the window, its content is immediately repainted.

(In reply to Christian Stadelmann from comment #2)
> Also, when moving the window, its content is immediately repainted.

Having this issue as well. Under wayland window repainting doesn't work most of the time until window loses focus. When it works, it works only for a split of a second.

I cannot reproduce this issue any more with firefox-wayland-55.6-1.fc26.x86_64 from Martin Stransky's firefox-wayland copr.

Seems to be fixed now, Thanks.