Concerning 2), can you provide me the *.DD and *.RUN files to be able see what's going on and answer the question?
Concerning 1), I can try to answer that if 2) will be cleared.
[EDIT:] I tested myself with your earlier example model but with a longer model horizon and investments into new electrolyzer capacity, and I am seeing the partial load efficiency losses for the newly invested capacity, just like for the existing capacity. Thus, I am not able to confirm your findings, sorry.
Concerning 1), I can try to answer that if 2) will be cleared.
[EDIT:] I tested myself with your earlier example model but with a longer model horizon and investments into new electrolyzer capacity, and I am seeing the partial load efficiency losses for the newly invested capacity, just like for the existing capacity. Thus, I am not able to confirm your findings, sorry.