My dishwasher upper rack does not glide in and out easily anymore. Do you know what parts i need to replace it?

When pulling out or pushing back in the upper dishwasher rack it feels like it gets stuck a little halfway there. There is nothing in the way and it feels like it is the metal grinding on itself more so than anything.

I dont see the metal sliders having anything on them such as residue or buildup. And we ran white vinegar through the dishwasher the other day to see if cleaning it would help but that made the problem a little worse. It makes a metal on metal grinding/screatching sound.