The reuse function is very useful in preventing opening multiple instances of the same buffer, unfortunately the :noselect option does not work well with reusing window from another visible frame. The window with popup itself is not selected, but the frame where the window is located gains focus, removing it from the original frame and the original window.
It is my expectation that the :noselect option should prevent any changes in window focus.
This is the config I'm using:
(push '("*buffer name*" :position bottom :stick t :noselect t)
popwin:special-display-config)
(setq popwin:reuse-window 'visible)