In general electronics then only working at a certain angle does usually mean some kind of ribbon cable is fractured or a solder joint needs the aid of gravity to work (either by making a connection or preventing a short).
You can test speakers. Get a dead battery (important that it is dead, or if not then a suitable resistor) and throw some wires around. You can see the cone then move in response to it, normally done if you have a speaker of unknown wiring (seen a few car ones be this) as reversing the polarity will change the direction it moves and you can then pick wiring accordingly.