Dear Ben, you are not supposed to get it from HEAD 😊. To my knowledge OpenACS releases are consistent. If you get something from HEAD, HEAD packages are required, if you are getting something from oacs-5-3 packages from there are required.
You should never touch or install any package that has a release number higher than the current release. If unsure, check it before installation. We had some problems with installing from the repository, but as you mentioned you did nothing, I am buzzled how you managed to get the code from OpenACS HEAD. For sure ti should not be downloaded.
So all in all it is not an installation issue, it is an issue where did you get the code from, as acs-mail-lite is not randomly calling OpenACS website to retrieve packages out of it's own release branch.
