With git-lfs sources, when a multipipeline job is triggered by a PR, it attempts to merge git-lfs files even though they are unchanged, and the PR build fails.  The lfs files in question are .png, and are never modified. 

The only workaround has been to set the job to build only the current pull request revision, which means that the PR will not be built against any valid changes made to the main branch while the PR is in development. That's not ideal.