Without divulging too much information, my dh needed to take care of something at MPF for his retirement next year. Turns out there was a conflict with his last re-enlistment as to what he SIGNED and what was in their system.
He brought in his copy, the woman looked in the system and compared them. The section in question had a DIFFERENT FONT style than the rest of the contract. Basically, someone went in and CHANGED the information AFTER everything was signed.
Hooray for keeping copies of everything. But be aware - keep a copy and keep good records.