Units in Tunnels/Tubes can be shot at, OpenTopped units inside can shoot out

[C&C Dune Mod]

Units inside tunnels/tubes: they can get shot at (though they're not harmed), and if they're OpenTopped their passengers can shoot out (they CAN damage and destroy).
You normally don't notice since tunnels/tubes have height 4 tiles from entrance to exit.

But that's a design choice, and sometimes map makers will have an entrance, use slopes to back down 4 levels, then just before the end go up 4 with slopes and then ending the tunnel/tube.
Others are crazy and have a tunnel/tube exit/entrance on a level, the other end on another, like 4 levels higher/lower.
These design choices make this bug manifest.

[mevitar (mevitar)]

This is an issue with the subterranean locomotor, which wasn't properly updated in RA2/YR, and thus, radiation and open-topped don't work correctly with it. Units in tunnels also use that locomotor and have to suffer from same issues/limitations.