The latest version of Flamingo 5.5 hangs up Rhino 6.3 on every Flamingo tree (small, medium, or big). The Flamingo render window says that rendering was completed, but there is no way to exit the window or to save the rendition. When I close the render window, Rhino hangs up, as shown in the following screenshot.

The latest version of Flamingo 5.5 also hangs up Rhino 6.3 when Flamingo control panel is turned on, and I click on one of its tabs while the control panel is still loading some tabbed panels. Groundcover works fine.
I tried to install older version of Flamingo, but it seems to be impossible - the installer displays routine messages, but the installed version of Flamingo does not change.
(The quality and speed of native Rhino 6 renderer are superior to the quality and speed of Flamingo renderer. The only reason to use Flamingo are Flamingo plants.)