Duplicate device names in the admin console

I have come across several instances where a device has duplicated itself in the console, i.e. the same name shows up twice. The only difference between the two is that one device was last activated at an earlier date than the second device of the same name. Talking to IT all I can find is that those machines have been re imaged at some point.

I read somewhere that the device license doesn't need to be reinstalled when a computer is re imaged but it now seems to me it needs to be both unistalled and reinstalled to avoid the issue of duplicates in the console. The problem is of course that they take up double the amount of licenses. What would the correct procedure be if a computer need to be re imaged, or is there some other reason this duplication happens? Can I simply deactivate the older duplicate or will that affect the newer version?