Is Use Of M12 Connectors For Lift Cameras Essential For Good Stable Performance Or Is RJ45 Connector Adequate?

For an elevator cab, the continuous movement warrants using M12s, because a service call just to reconnect a loose connector is especially difficult.

M12's often use screw threads to be connected, while RJ45 simply push into place.

The mechanical screw and multiple pin interface means the connection point withstands vibration and movement better. 

Using PoE cameras with those connectors or adapters can be a problem to be aware of. Especially if adapters are used, the negotiation process between the PoE source and the camera can be interrupted so negotiation will not happen.