Tracking link dont work

Hi

Almost none of the tracking links that customers receive work. funny enough we can track the packages using the links from the emails that customer receive wihtout issues, yet on customers end it never works, usually it sends them to a shipment from few months back or they get an error saying the tracking number doesnt exist. we have to track the packages for all customers ourselves and send them emails with screenshots, this makes our life hell. please advice!
thanks