I wonder if the show is still having any re-writes. If that is the case, it is very hard to remember lines if you've received them say a few hours or even a day before the show. I don't know if they are still re-writing or not.
While I'm not saying it's an excuse, in your eighties it is very hard to remember a lot of lines, Ms. Redgrave is in her early 70s, and a lot can happen in 10 years with the mind. I think it is great that Angela, in her eighties is returning to the stage. We should be grateful, even if the written show isn't worthy of her or Seldes or anyone else.
"Love the Art in Yourself. Not Yourself in the Art." -- Stanislavski