In the event a Raisin partner bank or credit union fails, your funds would likely be temporarily frozen while the FDIC (in the case of a bank) or NCUA (in the case of a credit union) works toward resolving the failure, including by determining eligibility for deposit insurance (typically within a few days of the bank closure) or through the purchase of the failed bank by a another bank.
In the event a Raisin partner bank is sold, you would still have access to your funds; they would just be deposited at the purchasing bank. You would be able to then deposit or withdraw your funds as needed.