How do you open the cages with echos inside?


I am in the tyrant mines at the academy ruins. The current quest is "Silence the relics". We have already found 8. So it says echos delivered 8/12. We have found the remaining 4 echos but they are locked inside these metal cages. The cages don't appear to have any way that they can be opened. 

There are some boxes with red lights on the side but they don't do anything. How do you get these open? Scars just keep spawning making this quest seem impossible.


I think you have to clear the waves of enemies that randomly spawn over time. I was stuck on this too and at one point I flew back to those cages and the lights had turned green and I was able to open them. Maybe someone found a switch or something