Without knowing the details of your story, I would guess your instructor marked the whole scene as “redundant” because the scene was a rehash of a previous scene. The specific actions changed, but the scene’s purpose and revelations were similar to the earlier material. This is something I commonly see in writing workshops.
For example, Joel and Winnie are in line at the grocery store. Joel eyes the young woman in front of them and is quick to help her get the bag of charcoal from her cart to the counter. This irks Winnie and she doesn’t talk to him for the rest of the day. Later in the story, Joel and Winnie go out for a nice meal and want to share a bottle of wine. Joel wants white. Winnie wants red. They bicker. Later in the story, Joel and Winnie are staying in on a Friday night. Winnie chats on the phone during a television program Joel wants to watch. He fumes until she’s off the phone and then mopes the rest of the evening. Enough is enough, already. The reader gets it: Joel and Winnie get on each other’s nerves. The reader doesn’t need three different scenarios to understand this. One is enough. The others are, as your instructor might say, redundant.
If you’re simply rehashing what’s already been established, the story will lose its momentum. A scene may reinforce what has come before, but it should also contribute something new. Perhaps Winnie says something unforgiving in one scene and Joel debates whether he’ll do the same back. They may still bicker in the next scene, but it has a new purpose: What will Joel do in response?
Is there a way to make your “redundant” scene less redundant by adding something new? Perhaps so. Or…perhaps you have already done that and your instructor just missed it.