After getting lucky and opening all available nodes on Europa and the Moon, I can no longer use the resonate stems through the Resonance Amp any more. It just says they can be exchanged for other items in the HELM. I want to clarify as to whether this is a bug or intended. I was able to get 2 deepsight IKELOS weapons from these node chests so not being able to continue this is slightly annoying. Now I have to use the Ikelos weapon focusing which requires an umbral engram and 25 shards on top of the 4 stems.