The first time I opened VR3, it opened in one of those titlebar-off-screen floating windows. When I tried to toggle it off, Leo spewed out a continuous stream of the following:
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
After I closed and reopened Leo, I used the new command vr3-use-default-layout and then VR3 opened normally in the right-hand panel. After that it continued to open and close without errors.
Note that this was using the version of VR3 in the layout2 branch. Using my own slightly modified version, VR3 opened and closed correctly, including when a floating window was opened using the splitter context menu.