I am not sure if this is a bug or not, I can only shift-click upgrade the solar neutron activator from the base not the top part with the solar panel.

This could just be an issue with the way the game handles objects that are a single entity, but sit within more than one block space. Similar to how the Digital Miner works.

By the way, I'm at a loss to find any information on this "upgrade" for the SNA. I've seen it listed somewhere else as well. Could you elaborate? Is it in a beta update?

see #3487