#+cite_export: csl ~/Templates/csl/AGLC-intext.csl

where AGLC-intext.csl is a custom csl file.

Exporting to html gives this error in *Messages*:

citeproc-s-slice-by-matches: Wrong type argument: stringp, nil

The error does not occur with different csl files.

Is there some way other than bisection that I can find the citation that is causing the error?

Emacs 27.1 on Debian stable.
Org version 9.5.4 from Melpa-stable

--