Oh, sorry! I forgot to mention this important information.
I’m using the EI9 (no compatibility mode)
If I click on the combobox, the list open and closes immediately when I release the mouse button, so that I can’t select something. If I click on the combobox and select the desired option without releasing the mouse button, I can select one option, but when I release the button the list closes and the old option returns.
But, if it works with Firefox, I can use this browser for this. No problem.
(with Firefox works for me too)