Not only this add-on, I think every SNPC based on VJ Base made by you doesn't respond to attack of friendly 'npc_turret_floor'. The SNPC is immune to the turret attack, while the SNPC attack and destroys the turret.

I tested with Rebel 'npc_citizen', and your SNPC took damage from them.
But it didn't take any damage from friendly 'npc_turret_floor'.