That happens all the time.
FCC website is what the government authorizes/has authorized. Infrequently, there are mistakes made. Just because it is licensed one way, doesn't mean that it is being used 100% accurately to the letter. Licensed party changes happen, operational situations or physical changes in systems happen daily. People even file licenses with dubious information or under an STA to put up a system that was previously denied based on merits. It is not foolproof.
The RR database is solely based on user submitted data. If it is not submitted, submitted incorrectly and not caught, misinterpreted, etc...it will be incorrect.
They seldom match up 100%. One is in an ideal world where everyone follows the rules, and the other is what the users see.
If you see something different, you make a submission regarding the frequency & site in question - with your supporting evidence, and a responsible party for that region will process it for you. They might have additional information about what they know, as opposed to what you think you see, and they'll address it.