Revealing mistake: In the dance off scene when Rose is doing cartwheels, you can see it's Betty White's stunt double.
Other mistake: In the 1954 flashback scene, it is Dorothy's 10-year anniversary, so she got married in 1944. In another episode, Dorothy said Stan impregnated her in the back seat of a car by saying he's going to the Korean War, which began in 1950. Also, viewers know that Dorothy went to college. A pregnant newlywed in 1944 with a husband off to war would not have gone to college but stayed home awaiting the birth of her child. And in 1945, after the war, she would have been a housewife, not a college student.
Suggested correction: First off, I don't remember the show every showing or saying Stan did serve in the military. Dorothy said the only reason she went out with him was because he claimed he was being shipped off to Korea and would probably die. Stan was shown not to be faithful and probably not very trustworthy. But there's no reason an intelligent woman with a child could go to college even if her husband was in the military.
Plot hole: In the flashback, neither Dorothy and Stan nor Sophia and Salvatore own a TV yet. Still, Sophia knows exactly what shows each of the four like. It's unlikely Sophia regularly watched TV before as Dorothy believed her when she lied about thinking a TV is a waste of money.
