The following minimal example

\definefontfamily[mainface][serif][TeX Gyre Termes Serif]

\setupbodyfont[mainface,15pt]

\setupnotes[footnote][bodyfont={mainface,12pt}]

\starttext

text\footnote{Still more} and more text\footnote{And then again}

\stoptext

gets the size of the first note at 12 pt but sets the second at 15pt. How
can I fix this?

Alan