enki71,

You are hit by a random unsolved bug that has affected a few people before

I can only suggest to try to use SMS backup from N9QTweak to backup your messages and read the .csv files on your PC to see if the smses are all correct then do a tracker reset (tracker-control -r) and then restore the messages. A tracker reset also deletes all your contacts and call logs so always backup your contacts first and disconnect from the internet before resetting tracker.

If you aren't sure about tracker reset ask but first get your messages out and see if they are attributed to correct senders.