Reporting this bug here as I haven't been getting to it in the last few days, in case somebody else could look into it.
@ is supposed to be a line continuation character inside @deffn, but the following gives an error "unexpected @": @deffn {Public Function} count_records (@var{start}, @ @var{end}, @ @var{record_id_vector} = 0]) @end deffn (From "IWF Metadata Harvester Manual"). I couldn't see what was wrong with this so I assume there must be a bug in texi2any.