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