If a bank purchases a loan (e.g. via a branch acquistion) and later on discovers that the loan has a reimburseable TIL violation, is the purchasing bank liable to the customer?

This could easily be a holder in due course issue. Often there is a buy-back agreement for these scenarios to protect you.

I had a similiar question about this. If a Final Truth in Lending was wrong, and a new one issued to the customer, should we require a SIGNED corrected final TIL? Thanks.

If you send corrected TILs it is a good idea to request it, but not necessary.

Keep in mind if your original TIL had a reimbursable error, sending a corrected TIL does not relieve you of your reimbursement liability.