I also have two 880s. BOTH somehow wear the ridiculous mirror coatings off the bobbins. Quilt Beginnings used to allow us to exchange, but no longer. Bernina insists they have fixed the problem, but it still exists. My one 880 is only 2 years old, my other one is 4 yo.
Extremely frustrating. I am going to exchange one of my 880s this summer. Not sure what for yet, but as much as I love my Berninas, I'm disappointed with their poor customer service.
Currently I have two 770s, two 880s, and one 790.
At this moment, my newest 880 won't release the Bobbin... *sigh.