Can't select hybrid height variable in xconv2

[bnlawrence]

This file:

Data            : northward_wind(atmosphere_hybrid_height_coordinate(85), latitude(1921), longitude(2560)) m s-1
Cell methods    : time(1): mean
Dimension coords: time(1) = [2014-04-16 00:00:00] 360_day
                : atmosphere_hybrid_height_coordinate(85) = [0.000117647105071228, ..., 0.9652941823005676] 1
                : latitude(1921) = [-90.0, ..., 90.0] degrees_north
                : longitude(2560) = [0.0703125, ..., 359.9296875] degrees_east
Auxiliary coords: model_level_number(atmosphere_hybrid_height_coordinate(85)) = [1, ..., 85] 1
Coord references: standard_name:atmosphere_hybrid_height_coordinate
Domain ancils   : id%UM_atmosphere_hybrid_height_coordinate_a(atmosphere_hybrid_height_coordinate(85)) = [10.000003814697266, ..., 82050.0078125] m
                : id%UM_atmosphere_hybrid_height_coordinate_b(atmosphere_hybrid_height_coordinate(85)) = [0.998870313167572, ..., 0.0] 1

results in two vertical coordinates shown, and selection deos not work.