[NTG-context] vertical offset with "i" in position-command

Hi, When I want to type an "i" in the position-command, there is some vertical offset: \starttext \startpositioning \position(1, 1){i} \position(2, 1){x} \position(1, 2){x} \position(2, 2){i} \position(1, 3){a} \position(2, 3){x} \position(1, 4){x} \position(2, 4){a} \stoppositioning \stoptext Why is it so, and how could I avoid that please? TIA for any hints, -- Peter