Custom plan variables do not seem to resolve to their values consistently when generating a release

I have plan variables to store the major and minor versions separately, as our deploy scripts handle major and minor upgrades differently, and the variables only seem to resolve to their value half of the time when generating a new release. Funny thing is, the variables always seem to work right when I click preview on the Release Versioning page.

To reproduce, add a variable to plan, say build.foobar = works, run the plan and then attempt to make a release out of it using the variable ${bamboo.build.foobar} in the release name. It will work in the preview, but it will frequently not work when generating the release. As far as I can tell there is nothing different happening when it works vs. when it doesn't.