Other mistake: When Ricky and Fred hold up the newspapers with the big holes in the back page, we see the front page with the headline "Bond Issue Defeated", and it should look familiar since it's the same front page that was used in the episode "Ricky's Old Girlfriend", with the article about Carlotta Romero. (00:18:15)
Character mistake: After Ethel chooses the ladies who'll play instruments for their own orchestra, Fred enters the Ricardo apartment with muffs over his ears as off-key plucky piano is heard in the background, indicating Ethel is playing very badly, when in all prior episodes she played fluently for any of their show warm-up numbers.
Chosen answer: It's not known. She may have moved it to the spare room or it may be in a corner just off camera. There could be any number of reasons, though it probably took up too much room on the studio set, and it was removed, making it easier for the actors to move around.
raywest ★