Got a follow up email from Eric Sampson - definitely appears to be a torque issue which is too bad. He looked at the photos and confirmed that. I'd love to find another set in 170mm or 172.5 but am doubtful that will happen. I'll also keep an eye out for a Topline. Talked to my dad earlier and he'll definitely want to go with a lighter weight crankset.

On a side note - I had to tighten the bolt on the left arm the other day as it was creaking but don't think I tightened too far. I could have - it's hard to say. I didn't touch the right side arm so I know I didn't cause that problem.