super() treated as undefined when a Lua-modified action is called from another function

If a lua-scripted action is called by another lua function, attempting to call super() inside the action will print an error such as the following:

WARNING: ...Addons\Skins\cl_Shadow-v1.2.pk3|Lua/SHADOW-MOTOR.lua:775: attempt to call global 'super' (a nil value)
stack traceback:
    ...Addons\Skins\cl_Shadow-v1.2.pk3|Lua/SHADOW-MOTOR.lua:775: in function 'A_RingBox'
    ....19.pk3|Lua/Objects/General Objects/Obj_Monitors.lua:103: in function <....19.pk3|Lua/Objects/General Objects/Obj_Monitors.lua:82>