When Tony and Meadow are arguing in Meadow's room, the gold charm/medal on Tony's necklace is alternatively inside, then outside of his white t-shirt.
When Davey lays down his hand in the poker game against Silvo's three-of-a-kind, he claims to have a flush. He shows a 9 of clubs, 10 of hearts, 5 of hearts, ace of clubs, 9 of hearts, jack of hearts, and a queen of spades. You need five of the same suit to have a flush, e.g. 5 hearts, 5 clubs, etc. Davey only has a pair of 9s.
During the scene where Furio talks with the motel manager, the second hand on the clock behind the manager doesn't move.
Meadow Soprano's friend plays a bass riff while Meadow sings but his left hand's fingering on the bass neck does not match the tune we hear.
Why were Tony and Riche talking about not paying back the vendors in front of their delivery men? The delivery men could simply tell the vendors they're not going to get paid for the items they're shipping.