Tray icon menu doesn't show sub-menu (Dropbox, fcitx)

[Peter Great]

I'm currently using Ubuntu 19.10 with the default gnome desktop. I have problems with some software which shows small icons on the top right of the desktop, next to the power and wifi buttons. For example, when I click on the Dropbox icon to expand the menu, and then click "recently changed files" to expand the sub-menu, the sub-menu listing the new files only appears for a fraction of a second, then collapses by itself before I have time to click on any entry. I also have the same problem with the icon for the fcitx input method.

I don't know what causes this. Does this have anything to do with GTK / QT themes?

[Peter Great]

After more searching on Google, I found this to be a known bug in Dropbox:
https://www.dropboxforum.com/t5/Drop...10/td-p/392201

There is some workaround, i.e. installing 32 bit instead of 64 bit version of Dropbox, but it seems too much of a hassle to be worth trying, at least for me.