"Add to my playlist" button not working. The square black box that say "add to my playlist" seems to be obscuring the actual "+" button. 

If the file has more than one or two tracks, if you try opening the player in it's own tab you may be able to shift the position of that box by scrolling up and down the list slightly with the arrow or mouse wheel.  That box can can be removed in firefox though and maybe other browsers by downloading something called uBlock origin (an ad blocker) and then opening the inspector by right clicking the box and then clicking "inspect".  Next you right click on the element highlighted and then choose "delete node".  This should delete it once per occurrence.  At least it worked for me.  Try it and tell me what works.