Unable to Change Target Branch

I'm trying to edit the source control settings to point cloud build to a different branch but when I get to step two, granting access to source control, I'm told the repo is inaccessible. I've already added the SSH key and I was able to get past this step in the initial setup of the project in Cloud Build.

Checking the detailed build log of my latest (failed) build, it seems like the cloud build system is able to access the repo from that side at least, I'm not sure what I'm doing wrong that I can't change the source control settings for the project.

 

For reference, it seems like collaborators are unable to change the target branch. Changing the target branch from the account that created the project worked.