After TEIP5-Documentation and TEIP5 failed to build again, I went in and looked at the logs more closely. I think the failure is caused by the absence of the Deja Vu fonts, which would of course be installed by default on a desktop but are not there on the headless server. I've installed them, and added them to the script, and I'm running TEIP5 again. There may be other common fonts missing, so we might have to go through this process a few times, but this is definitely progress.