If you usually have multiple drawings open at the same time. During this time, the command line quits accepting input, and if you switch to another drawing you have open, you see your commands there.
This is related to AutoCAD Civil 3D's Autosave changing focus to a drawing that's open, but not active.
There are two workarounds:
1. Turn off Autosave (not recommended)
2. Type in LEVELOFDETAILOFF, which will turn off the level of detail, and prevent the Autosave from changing focus.