How to use the Culverin properly?

Can anyone please tell me how to use culverin properly?

On hill and dale, I am on top of the hill, no wall, cliff or any object between enemy bombard and my culverin… Clearly visible, line of sight… I click it exactly with right mouse button, I see the red circle indicator…
The unit starts to move towards… ok, I think it´s out of range first… but no, next time I look, it`s just reached the enemy infantry. What am I doing wrong? (Except that I went away to look at something else…)

Might have been a misclick, culverins work fine on my end.

Another option is that the enemy was retreating the bombard you wanted to destroy thus the culverin kept chasing it.