.@manton here's some strange I'll try to get to the bottom of tomorrow.

With the previous theme reinstalled, everything builds … and the harmless errors are spawned by my conversations plugin.

With the latest theme version installed, the errors are no longer logged…

and it looks like everything builds (tags from homepage head)…

but … if you check the head tags for a post page…

the previous theme version's pages are there. It will be interesting to see if this new post will be permalinked … because it seems like what most likely happened was that everything looked right until I triggered the full rebuild for the first time with v180 installed.