The Support module broken for artillery (virtual and unit placed). Get the same error trying to call in mortar on Campaign mission "Radio Silence"
For virtual Mortar get 2 entries in the available support
both gives this error
'..._roundsLeft + (_x select 1)};
}forEach I#I_curAmmo;
]forEach _batteries;

_rounds...'
Error Undefined variable in expression: _curammo
File A3\modules_f\supports\procedures\calculateAmmo.sqf, line 29

For sandstorm and scorcher doesn't return an error message - the virtual support will appear but fire mission will not occur.

For placed arti supports you get the same