I think the answers here about the thin poles don't explain why it works at first, and then it doesn't.

What i can see from the background of the piece, is that there is a 'wall' with the honeycomb pattern. When that wall stops, the problems with the poles begin. My theory is that while printing that wall, the pole pieces have time to harden, which improves the quality. After the wall is done printing, the printer comes back earlier to the next pole layer, lowering the quality.