I found a bug!

I have one PNR, with 2 of the same flights, same flight numbers, same routes, but different days of the month. I cannot get my seat assigned in the app because it mixes up the 2 legs.

I click one leg during seat selection, and it loads up the seat map for the other. And then I select my seat and it doesn't stick/save. I click the other leg, and it loads some random seat map again. Basically, it doesn't behave correctly because I think having the same flight number AND the same routing is confusing the code.

Where can I formally submit this defect?