About the same happens on Ubuntu 17.10 wayland. After logging in account, I see Dropbox icon, but clicking on it has no effect at all until I double click it. Then undecorated white menu appears at current mouse pointer position and there is no way to close it apart from clicking some of the menu items. After that clicking Dropbox icon starts working and a decorated menu is displayed.
About the same happens on Ubuntu 17.10 wayland. After logging in account, I see Dropbox icon, but clicking on it has no effect at all until I double click it. Then undecorated white menu appears at current mouse pointer position and there is no way to close it apart from clicking some of the menu items. After that clicking Dropbox icon starts working and a decorated menu is displayed.