Every dropdown list does not work with mouse, only with keyboard.
Clicking in the scroolbar of the dropdown list close the list, clicking in an item in the list does not change the item displayed in the field, but the selected item changed.
Versão (version): 18.104.22.168 (x64)
ID de compilação (compilation ID): bcace328aabc4c8c10b56daa87da0a2ee6579b5a
Threads 4; Ver: Windows 6.19; Render: GL;
Local: pt-BR (pt_BR)
Windows 10 single language pt-br
Thanks for reporting. It's already fixed towards RC2.
*** This bug has been marked as a duplicate of bug 96119 ***