It seems if I travel too far in space maps, I just disappear and it says I died.
Flying in those areas is not an issue, only when you're on foot do you die.
Can this be fixed?

Which space maps?

I know that many space maps have a SetWorldExtents(someNumber) line in their mission script. Try increasing the number or commenting out the line.

Reminds me of the terrain height issue I'm suffering, although need to do more tests with .MSH as the "MATTE" for the "PAWN", instead of TERRAIN.

*edit*
My issue is likely unrelated; but I'd try putting the pawns on .MSH instead of the ZE Terrain; see if that changes the conditions. I will have to test this eventually, hope this isn't a "Space Map Bug" for troops.