One of the ways sandbox gadgets work is we delete the windows (popups) if they are unfocused... However if the windows contain a list, they are immediately unfocused and therefore get immediately deleted and never shown. Suggests that windows that have lists get unfocused immediately.
near the same for elm_entry. the popup is not immediately deleted but a click in the entry closes the popup
also with elm_check and with elm_colorselector but there only if you use the arrow buttons to change color
maybe with more but i have not tested