Apple II keyboard replacement: MM5740-AAE with wrong marking?

Hello. I'm repairing an Apple II keyboard, where I needed to replace a defunct MM5740-AAE/N. I bought a couple of new MM5740-AAE/N from Littlediode, they arrived and have a quite modern aspect and National logo, while the old broken IC has no logo. Maybe they are coming from a more modern production... I tried both on the keyboard, same behaviour: the keyboard itself works, but I receive wrong key codes from it. I checked with another keyboard, computer is working fine. I double-checked the MM5740 marking, it's absolutely correct. Of course I checked for sticky bits, or logic problems, but nothing strange there. I wrote down a key "replacement" table, and from what I see these AAE encoders are generating codes exactly like they was AAD version... Maybe here there's a problem of wrong markings over the ICs? Anybody ever heard of similar issues, or bought these encoders from Littlediode and had similar problems? I suspect that they came from a production lot wrongly-marked. Andrea