You must compare the old contract with the new supplementary agreement to see if there are any new clauses that are unfavorable to you.

I know ABC has renewed the contract, but the old contract can still be used. I asked the mortgage department, and they didn't know what the new supplementary agreement was. I guess your local branch came up with the idea itself.

I feel that if there is a problem, it doesn't matter if you don't sign it. Anyway, the money has been released and you have paid it back normally. The bank has no reason to come first, and they won't sue you!