Hello.
I bought a car from a trader and brought it back to my base. Logged on the next day and it was gone. No one stole it as it was locked in the garage that I made. It had not been broken into or any loot taken. It despawned. I also found a car and repaired it. Brought it back to my base and the same thing happened. Seems to me that this has been an issue with Dayz for years now and it is a major down point of the game. Plus driving and shifting through the gears is so stupid. Cars despawn. Such a shame given the work involved in acquiring one.