[NTG-context] \switchtobodyfont behaves differenctly with splitted parameters

Dear List, after hours of debugging, I finally found out that \switchtobodyfont[face, 20pt] does NOT behave the same with \switchtobodyfont[face]\switchtobodyfont[20pt]. In my case the latter is the correct one, while the former does nothing but falling back to latinmodern. Does anyone know when or why \switchtobodyfont behaves differently with splitted and joined parameters? Thanks. Best, Sylvain