Hello,

There is a numberconversion problem in caption prefixes. For instance, if
chapter numbers are set to Romannumerals, the conversion of the caption
prefixes depends on the presence of a section

Minimal example:

\setuphead[chapter][conversion=Romannumerals]
\setupcaption[way=bychapter, prefixsegments=chapter]


\starttext

\chapter{Cool}
\placefigure{A cow}{\externalfigure[cow]}

\chapter{Cat}
\section{Mouse}
\section{Dog}
\placefigure{A cow}{\externalfigure[cow]}

\stoptext


The previous code displays an inconsistent caption prefix (first time a
Romannumeral, second time a number):

I Cool
[figure] Figure I.1 A cow

II Cat
2.1 Mouse
2.2 Dog
[figure] Figure 2.1 A cow