On my system (Debian) the helper app frequently stalls and there doesn't seem to be a way to kick it.

I also have another problem with the author(s): I frequent a (for-pay) web site on which this add-on didn't work. The author rejected my offer to use my account for testing. OK, I can live with that, so I found a free video which exhibits the problem and added a comment with the link. That comment was deleted from the forum, without notifying me. So was a follow-up message asking for an explanation. (Politely, I should add.)

Sorry, but this is not acceptable.