Continuity mistake: When Nancy is in Doug's office, the items on his desk change position in between shots. (00:04:20)
Continuity mistake: When Nancy sees the video tape of her husband, the items on the table vanish in the next shot. (00:27:50)
You Can't Miss The Bear - S1-E1
Continuity mistake: When Josh and Nancy are driving in the car, the arm rest on Nancy's side keeps changing position. (00:08:55)
You Can't Miss The Bear - S1-E1
Continuity mistake: When Nancy goes into her guest room with Silas and Quinne in it, the things she are holding change position in between shots. (00:28:35)
Answer: It's not uncommon for TV shows to suddenly "age up" baby/toddler characters in order for them to have more narrative purpose. Other examples of shows I can think of that did this are "Step by Step," "Last Man Standing," "Boy Meets World," and possibly "Dexter."
Phaneron