Getting the error: {"error":{"code":"OperationNotAllowed","message":"Fields that were already present in an index while updating Index

Question

I am trying to update an Index and get the error:

{"error":{"code":"OperationNotAllowed","message":"Fields that were already present in an index

This Search index was backed up and restored from another index. When I look into the schema of this index now, it has the suggester name with the prefix of the original search index(the one used for backup). Is this the real issue or something else?

Also, how do we resolve this? When I try to update the prefix of the suggester to use the name of the current index, it throws the exact same error.