When Mother breastfeeds her baby, during one shot, she has a scar on her forehead. During the next shot, there is not a blemish on her face.
When Woman brings Mother some lemonade, the ridges in the plaster change between scenes.
When the Michelle Pfeiffer's character burns her hand on the skillet, her husband tells "Mother" to get some ice. As a medical doctor (he said earlier that he is a surgeon) he would know that applying ice to a burn can further damage the tissue. It would have been better to run her hand under cold water.
The first time Mother calls 911 and hangs up after it was answered, the 911 dispatcher doesn't attempt to call back. In reality, 911 would immediately call back on a hang up call.
Around the beginning of the move (near 13:00), the furnace, which appears to be an antique from the early 1900's, turns on and lights up mysteriously on its own (such a furnace would be manually lit), but makes the sound of a natural gas furnace.