Other mistake: It's raining outside. Dorothy comes in the house and says "it's really coming down", then shakes her coat off although it's not wet. Then Stan shows up with an umbrella that's not wet. Then Sophia's brother Angelo shows up and isn't wet either.
Continuity mistake: About three minutes into the show Dorothy, Sophia and Stan are in the living room. Sophia is trying to convince them to pretend they are still married while uncle Angelo is visiting. Dorothy is wearing a large pair of earrings, but at one point during their discussion when they show a close up of her, the left earring is suddenly missing. A second close up shows the earring still missing, but as Dorothy turns her back to the camera, she reaches up and touches the remaining earring. In her next close up, she is wearing both earrings again.
Factual error: Angelo claims he promised their mother on her deathbed that he would become a priest, and Sophia says she promised she would marry someone else - and we assume she died before Sophia or Angelo got married to their spouses. However, in the episode where they are flashing back for Mother's Day, Sophia's mother is in this episode along with Sal (and she looks like an older version of Dorothy).