ive had my main guitar a telecaster 72' deluxxe reissue for about a year
and recently its developed a problem

when i have the selector to the neck and bridge, notes played are acompanied by a harsh crackleing sound, said noise gets louder if i play louder and softer if i play softer

its still under warrenty so i should be able to get it fixed for free (even if sound control - the shop i bought it from - has closed down)

but what im here to ask is what exactly is the problem? so i can explain to them what needs to be done

thanks in advance
sounds serious, is it repairable? or will a new pickup be required?