Yes, I am disappointed with my manager, especially given the number of times and the insistence with which I've raised this. It's clear to me both that he's afraid how this will reflect on him to his manager, and he's afraid of how the other engineer will react. He wants to keep the peace, which means me just sucking this up.
I don't want to leave this job unless I've exhausted all other possibilities. With this exception, it's great.