lunar yacht
I failed to beat all five waves a few times and was like "I'll do it tomorrow" and played for a bit longer doing other things before saving and hopping off and after starting up the game and loading my save the gate is now locked as if I were inside.
The other two crystals are still on and I have now way of getting in or activating the third crystal now (I could easily hop inside, but invisible wall/ceiling stop me, so no alternative way in, but there are no enemies on the other side, so I'm not even sure that would work).
bright shale