I have a working custom board with KL25Z128VLH4. I am planning to move to KL26Z or KL27Z due to the lower price and additional features. I tried to populate the same board with a KL26Z128VLH4, but it doesn't work. It always show the message “Device is secured. Erase to unsecure?” and it never succeeds. I tried both OpenSDA and Ulink2 interfaces, but the results are the same. According to the reference manuals, there is no hardware difference to justify this behavior. Do you have any clues?