Problem with ImagefromXYZ


I have some simple data gathered from a metrology tool doing a raster. It is doing a 21 x 21 grid and collecting amplitude and phase information. The data is provided in columns with X & Y coordinates. The data is regularly spaced in both directions and there are no missing values in either the position or the data.

I am attempting to use ImageFromXYZ with the command. I have created to waves to hold the data and the counts
ImageFromXYZ/AS {PosX,PosY,Amplitude}, Amplitude_map,Amplitude_Count.

When I examine the data matrix wave, Amplitude_map, the scaling seems to be correct, but the data isn't. Some of the points have been mapped correctly, others not and some missing. When I look at the count matrix some cells are counted multiple times some not at all.

I thought this a simple exercise, what am I doing wrong. The experiment is attached.

Update: In looking at some of the gaps and double counts, it looked like to cells were being added together. The X range was from 10 to 16 in 20 steps of 0.3 and Y from 203 to 209 in steps of 0.3. I changed the X and Y to be 100 to 160 in steps of 3 and Y 2030 to 2060 in steps of 3 (PosX *=10 and PosY *=10) such that the step increment is no longer <1. That seems to put the data in the right place.

Does ImageFromXYZ not handle steps less than 1?
Raster Image.pxp