Incorrect members being shown in cluster in hac

Hi,

We have two environments prod , preprod . When prod db is refreshed on preprod env. , preprod env. Hac starts showing prod +preprod nodes in cluster monitoring console on hac.

This should not occur. Any pointers to where the problem can be. We have auto discovery turned on.

I can see cluster island id is same in both the environments. Any pointers on how to update cluster islandid?