Analysis board not loading a PGN

So the analysis board has a problem when it comes to making comments after moves. Once you get far enough in the game, the drop-down menu you get from right clicking on a move just disappears. If someone could tell me how to deal with that, that'd help avoid this issue in the future. Now, because of that problem, I downloaded the PGN, inputted comments manually, and then tried to reload it, but it doesn't work. The PGN shouldn't have formatting errors because it loads successfully on other sites, so all I can think is that chess.com requires more strict formatting. Or the analysis board is just buggy, I don't know. 

Edit: Okay solved the issue; I simply had an incorrect move in a variation. But I would still very much like to know how you can continue to comment on moves later in a game without the drop-down menu disappearing.