Headscratchers / The Play That Goes Wrong

• Near the end of Act 1, Dennis keeps repeating an earlier line due to a similar line cue from Robert, forcing the cast to restart that block of dialogue over and over again. And even when the former catches on, he keeps repeating the line due to not being able to remember the next one. Given that Annie, who was covering for Sandra as the Femme Fatale, was reading her lines from a copy of the script, why didn't she just let Dennis read it to get his next line?
• At the top of Act 2, we see Jonathan on the study level trying to wake up an unconscious Sandra, who was put in a bathrobe after her costume was given to Annie. When she comes back on stage after regaining consciousness, however, she's in her underwear. What happened to her robe?