It failed to load mods due to this error:
error whie loading item prototype "uranium-rounds-magazine" (ammo): Key "type" not found in property tree at ROOT.ammo.uranium-rounds-magazine.ammo_type. action
Modification: Base Mod > Industrial Revolution 2 > Krastorio 2

Aww, second this one. I had trouble getting Squeak Through to work at the start of the playthrough, but after the latest factorio update I'm stuck with this error message as well when running latest IR2 + K2 on the most recent Factorio experimental build. Might have to revert to stable factorio and see if anything's different.

Does this still occur on the most recent IR2 version?

It occurs with the current latest versions of K2[1.0.23] and IR2[2.1.0]

I've been disabling the "Rebalance damage and ammo" option in Krastorio 2 mod settings prior to installing IR2 as a workaround, since the conflict seems to be somewhere in there.

I have the same issue.

Lol, it's because Linver already fixed this for the next version.