Book generation not honoring notebook title override in _toc.yml

[bgalbraith]

We have a number of notebooks from a course we are trying to bind up into an html jupyterbook. The header style we used include two H1s in the markdown of the first cell e.g.

# Course Day X, Tutorial Y
# Tutorial Title

The default behavior is to extract that first line, but that makes for an unhelpful generated TOC in the HTML version, so we tried to override this in the _toc.yml with the title param, but it is not honoring this and still going with the first line. Digging into it a bit, it looks like this is true whenever there is anything other than a single # line in the cell.

Is there any config option or setting we can add that will ensure the override takes place, or is this a bug on the generation side?