There is a tab "off map artillery assets" that never shows anything, despite my counter battery arty fires at the enemy artillery positions that they had already found.

I guess its probably a bug.

This is the save file from the end of "The Squeeze Play" mission. If you press "End game" you can see ...

The 5th mission of the Soviet Campaign "Red Hammer" is bugged (at least on some PCs).
https://www.matrixgames.com/forums/viewtopic.php?t=377227

I fixed the campaign, reassembled it with the 5th mission which I renamed properly.

For those of you who are stuck at the last mission I also uploaded the ...