Recently closed an old CD and was charged the current Early Withdrawal Penalty instead of the EWP that was in effect at the time I opened the CD. They were gracious and promptly gave me a credit, but I would have paid double the penalty if I hadn't noticed. Keep a record of the EWP for each CD.
It was an honest error which was corrected quickly and graciously. The penalty was calculated manually by an employee who may not have even been at that institution when the EWP for 5yr CDs was changed a couple of years ago.
Many years ago a flaky local credit union was taken over by a strong CU with help of the NCUA, the federal CU insurer. The failed CU's records were incomplete or at least didn't all make it into the new CU's system. The principal of my CD was not in question, but the EWP was. I had to bring in the document that gave the details of my CD, which the new CU honored.
Keep your own paper records for each CD and check if you happen to close a CD early.