Plot hole: Delores is walking into the murder scene at the beginning of the movie just as Ernie is shot. Later, while she is being questioned, she tells the two detectives what the thugs said and did, yet, she was not eavesdropping or looking through the door.
Plot hole: In the scene where the limo driver gets shot, Deloris walks in just as the bullet is fired. She doesn't see what happened before, just the guy getting shot. However, when she is telling the police what happens, she tells them that Vince looks at Ernie and says 'Good night.' He did, but she wasn't there at that point.
Suggested correction: The only genuine mistake is that Doloris wouldn't see Vince looking at Ernie or Joey but as the office door is glass, she would be able to hear them talking. Example being when Deloris leaves and is standing outside with the door closed she can hear Vince telling Willy and Joey to bring her back for a talk or, if she runs, to "take care of it".
Except that she never stood outside the door listening to the entire exchange. As soon as she got to Vince's door, she didn't stop to listen to the entire meeting she immediately opened the door, walked in and witnessed the murder and nothing else. Plus, about five seconds after Vince says, "Say, goodnight, Ernie", is when Delores arrives.
To add, the only way for her to witness the entire exchange between Vince and Ernie was if she was standing in the room the entire time which she wasn't.