Siege Guns - Very Odd Behaviour

[JonS1]

In a N44 scen I'm currently working on I have changed some of the largest guns to be Siege Guns, since the rules for that type better reflects - I think - the limitations of these really heavy guns.

However, once I started play-testing it, the Siege Gun units seem to have essentially unlimited fires - not the two shots of other artillery, not the one shot that Siege Guns are suppossed to have, but essentially unlimited. I fired a couple of units over 30 times each (yes, thirty!) in a single turn, and only stopped as I felt that was probably enough to demonstrate a pattern.

In terms of replicating this, it only seems to affect fixed units (speed = 0). All the mobile units I tested worked as expected. With the fixed units, they display "Fire Ability 2" on the in-game display, but this never decrements, regardless of how often they fire.

Could someone please explain what I'm doing wrong, or if this is in fact broken?

Cheers
Jon