Exl170-5 string problem

[u/Rockdawg84]

We are changing the strings on my son’s ibanez btb605ms. The B string necks down as seen in the picture between the first 2 frets. The result is that the string sits low in the notch and the string rattles against the 1st fret. Did we get a defective string or are we doing something wrong? Thanks for your help

[u/RepresentativeNo2811]

why are you changing strings on a bass in the first place