Here is a really odd one that I have a simple workaround for, but for the life of me I cannot work out why this is happening. Is 'p' (or 'P') some sort of restricted letter in certain circumstances?
Here is the issue:
\startdocument
[metadata:author={Author name},
metadata:title={Psalms}]
And I get an error. Document will not compile. Any other initial letter than 'p' (in Psalms) does not produce the error.
So if I do something like:
\startdocument
[metadata:author={Janet Dawson},
metadata:title={~Psalms}]
Then I no longer get the problem. Which just seems to confirm the fact that it is the initial letter 'p' that is the problem. I can also change the spelling of 'psalms' (anything really, asalms, xsalms) and there is no problem, but of course that would be silly.
I have never had this issue before, so while it looks like 'p' is the problem (it can hardly be the Psalms!), it is possibly something else, but what, I would not know. If it helps, I am calling in that metadata:title in the header in the usual way, e.g.:
\setupheadertexts
[ ] [{\getmarking[chapter]\hskip1em \pagenumber}]
[] [ {\pagenumber \hskip1em \documentvariable{metadata:title}}]
But that should not be a problem.