Recent experience led me to write up an illustrated example, with a new model made just for the purpose, of what can happen around happy little things like pin connectors.

The complete write-up is published at
https://www.stonelakeanalytics.com/2019/07/07/connector-or-crutch/ 

Basically, there's a thin wall in an arm near a bushed joint. One of these results uses a pin connector, the other full contact.