My colleague asks me today, “why are my dimensions hollow and not filled?” I thought, maybe FILLMODE is not set. But that was OK.
It turns out that this can be caused by non-flat or “elevated” drawings. I.e. 2D drawings that extend into 3D space. Usually caused by UCS not being rotated properly and it being skewed into 3D space.
The solution is to change the UCS in the modelspace or paperspace viewport so it is flat and things should be back to normal!