If you load the page for a job, the rebuild last link points to specific, which is the last build at the time of page load. However, if the page is left open, other builds can be run in that time. This invalidates the link, since it is now no longer pointing to the last build.

The Rebuild Last button should point to /

/

/rebuild. This ensures it will always rebuild the last build.

I will submit a pull request, but after a quick glance, it looks like the change needs to happen in the RebuildLastCompletedBuildAction.getUrlName() method.