Originally Posted by
saddlesores
.... the new chain came
only with a pin partially inserted, requiring the chain tool to install. it did not have the
non-reuseable shimano kwickie link as with the last one.
There's a point you may be missing.
Since the chain came with a partly inserted pin to be pushed across, it's logical to assume that's the correct way to close the chain, and you'd be right. But that doesn't necessarily mean it's the correct chain for your drive train. What makes Hyperglide and later systems shift smoother, especially under load, creates side stress on the plates. Also chains for 7s and more have pins flush to the outside of the plates so they'll be narrower, leaving no margin for any spreading. That's why modern chains require special pins or connectors.
Looking at the photo, it looks like your chain didn't have flush pins, so it was a classic chain without peened rivet heads. OK to close with a chain tool, but not proof against the side stress shifting with Hyperglide causes.