Here's a photo of the vault as it was about to be sealed in October last year: https://www.nasa.gov/missions/europa-clipper/how-nasa-is-pro...

In the meantime NASA built a whole spacecraft around it and the craft went through numerous tests. If they'd have to undo and redo all of that, they may even miss the 2025 backup launch date. I'm sure NASA is very eager to seek other ways to deal with this problem.