So, I’ve had squeaky arm rests with my ergochair 2 since the chair was pretty much new. I don’t know if Autonomous has fully resolved the issue but I’ve come up with a cost effective way to fix it. It requires disassembling the arm rest to get to the adjustment/slide mechanism and taking out the two screws that secure it to the arm rest. Cut a section of the t-shirt to fit the center portion of the mechanism so it can curl around it. Poke two holes in the fabric to pass through the two screws. Then reassemble. See links to pictures.
For new production, Autonomous can use an abrasion resistant fabric like a Kevlar sleeve to feed over the center portion of the mechanism prior to assembly to resolve the issue (likely permanently). I looked and it’s about $2 per linear yard and it only takes about eight inches to fix one chair (four inches per arm rest).