I'm also affected by this bug when using Thunderbird but I've found a workaround: Unpin Thunderbird (right click on the icon and "Remove from Favorites"). After that you can still start Thunderbird manually, it won't trigger this bug any more when it is just a normal application (and not a "favorite" application with a fixed place in the Dock).
I'm also affected by this bug when using Thunderbird but I've found a workaround: Unpin Thunderbird (right click on the icon and "Remove from Favorites"). After that you can still start Thunderbird manually, it won't trigger this bug any more when it is just a normal application (and not a "favorite" application with a fixed place in the Dock).