Problem
Dimensioning does not work for all lines in sections.
Solution
From the projection properties, select "Accurate section"; after this, dimensioning will work.
If you want the program to always create section projections as accurate by default, change the settings:
File → System Settings → Edit → Administrator View → 3D – search for the keyword "sectionviewdefault" (near the end of the list) and set the value to 0. Restart G4.