Wool dryer balls are no more abrasive than are the tumbling clothes so they aren’t of concern. The bubbles probably are wrinkles and creases formed when the sheet metal was stamped into the bulkhead form.

The drum rotates counterclockwise so clothes rub against that area when lifted to turn over, for contact on the moisture sensor bars, and past the exhaust air intake grill.

Are denim jeans among your laundry loads? Indigo dyes are unstable and often impart a bluish stain to that area which may have an appearance of wear on the surface.

We have not washed denim jeans yet bc we live in the warm south. Just seems odd clothes could do this. I think I’m gonna have them come out since it’s under warranty. It seems a tad louder than normal too.

A drum support roller is below that area but I don’t figure how it could affect the circled area.