Note that override_weapon_target_prereq_action gets messed up every time the affected unit gets garrisoned.
i.e., your sniper will be targeting just about anything (even infantry casualties). Giving a direct-face command (such as the ability bound to A for HMGs, etc) will restore the override_weapon-target_prereq actions.
It doesn't make any logical sense, and I've no idea how to fix this, but that's how it is.
That's lame - another bug that needs fixing.
As a workaround, you could put the override_weapon_target_prereq_action into an interval_action to execute it every few seconds. That might help, but it's probably not very efficient. Better than nothing, though!

Germany

Updating everything by hand after every patch is already enough work!
cblanco ★
보드카 중대
VonManteuffel
Heartless Jäger