Contact the folks at PenFed and ask them to correct their reporting errors.
Seems like they're reporting one card this month, and the other the next month, probably just because somewhere in their system your accounts are mixed up.
Since the name (yours) and the social (yours) are correctly the same for both, the credit bureau simply accepts the information. TU can't change the information once they receive it, you're going to have to work with PenFed to get it resolved.
I'd contact them, tell them what's going on and have them look into it with you on the phone, then at the end of the conversation request that they update their reporting mid-cycle (basically, send a fresh report with both accounts correctly listed to the credit bureau) to clear out the mistakes. Hopefully once they've done this, and sent the new reporting, it will continue to report correctly moving forward. Something in the computer at TU doesn't like PenFed's reporting.
If this doesn't clear it up, you can perhaps get TU to resolve it, if you can prove with PenFed's help that they are correctly reporting two accounts for you. This will likely be more complicated, but in the end I suppose whatever you have to do to get it corrected is worth the effort.
