Hey there, i recently found that adding something to the playlist can be impossible if you navigate with a mobile browser (e.g. firefox for android) at the middle or rather top of a list, because the context menu is not displayed completely in some cases. Please see screenshot.
Found this thread, someone had the same problem with the app:
Will try in the next days, perhaps the same helps with the web frontend.
Not working… Still, if the screen is too small to have a scrollbar, the menu won´t display completely.