The lug is not at the same level as the other. If the lugs are bolted on, you can replace it. Higher quality panel manufactures sell the bus bars, and all other parts as replacements. Not sure how old that panel is.
There may be nothing at all wrong with it. Not sure where you are located. If you can, you can pull the meter and check all the lugs and connections. After that, you will be able to determine what is needed.