Artillery range error

[gustmic]

Hi!

I was just playing "Wacht Am Rhein" and I noticed that one of the artillery units said it had a range of 19 and it marks enemy units with a red crosshairs as it should.
But when the "attack window" comes up, my unit is not shown.
So I did some troubleshooting.
It seems as if the range is actually 16, instead of 19, because it works when I am within 16 hexes.

This was a unit equipped with the gun "10 cm sK18", and I think it has to do with the gun.
If needed, I can look up the unit (in and around Monschau, an orange/tan unit).