Technically, only two possibilities.
The hour hand is attached to the center wheel via a pinion (slip fit). See below for a simple gear train diagram:

Either the center wheel has a problem (in which case there would be more issues), or the hour hand moved on the pinion.
The later is a common effect if a watch experiences sudden decelleration (drop/impact/banged into a door jam) while the hand is at an angle towards the direction of the decelleration. If the force excerted onto the hand exceeds the coefficient of the slip fit, it will simply "release" and move. This coefficient is rather high (try to set or remove hands for yourself and you'll see), so it will take some force to move them, they don't just slip by themselves. Given that the Chrono hands seem straight, my guess is that the impact was either top or bottom of the watch, most likely a desk or table surface or door jamb, while the hour want was anywhere from 8 to 11 pm or 2 to 5 am. Check the bezel or solid end links, there may even be a small ding from the impact. Are you wearing your watch in bed while sleeping?
For a fix, simply remove the hands and set them again correctly. A competent local watchmaker should be able to do this for you, just make sure to check if all hands reset correctly afterwards and the date change is still correct (many so called "repair" shops have no clue and butcher a movement rather than doing it right). If your watch is 5 years, it should get a movement service, during which it will be completely disassembled, cleaned, inspected, assembled and lubricated, so the hands would get set correctly again anyhow. Also a good time to check WR and replace gaskets if needed (this should actualy get done annually) and it seems like she could use some cosmetic service as well (new bezel inlay, polish and brush of case and bracelet).
Where did you buy the watch?
Cheers
Matt