[NTG-context] Reduced whitespace when nesting different itemgroups

Dear list, I have noticed a strange behavior when nesting different itemgroups: The whitespace before the lower-level group is reduced. This does not happen when nesting itemgroups of the same kind. And this can somehow be circumvented by setting [columns, one], see MWE below. Is this expected behavior, or a bug? Best regards, Florian MWE: \starttext \startitemize \item Itemize 1. \startitemize[columns, one] \item Itemize 1.1 \item Itemize 1.2 \stopitemize \stopitemize \defineitemgroup[it] \startitemize \item Itemize 1. \startit \item It 1.1 (reduced whitespace above) \item It 1.2 \stopit \stopitemize \startitemize \item Itemize 1. \startit[columns, one] \item It 1.1 \item It 1.2 \stopit \stopitemize \stoptext