We've realized what the second issue is caused by. On web browser, we were able to open the secondary systems menu, but we had to click the arrow to do it. I'm guessing it's the arrow that triggers the menu drop-down, and that's what's making it an issue to open it on mobile, because the arrow is so small.
Would it be possible to make the whole text into the drop-down press, or in some other way making the arrow bigger?