Trouble setting radius from MP in Loiter flight mode

I have a quadplane that’s flying well in Auto, Loiter, Cruise and other modes. I have a problem that I hope someone can help with,

During forward flight, I can set the mode to Loiter and adjust the radius using the Set Loiter Rad button from the Mission Planner GUI. However, when executing a mission in Auto using LOITER_TURNS command, the radius value sees to overflow above 255 meters.

I see the same behavior in missions made and deployed from QGC latest.

Is this normal? I don’t see a value range in the Mavlink spec for MAV_CMD_NAV_LOITER_TURNS so I thought more than 255 m is allowed.

The vehicle is using Arduplane 4.1.0b as Quadplane.
Thanks for any thoughts,