I use ImageEn version 6.0.1 and this issue is not solved. I assume in this sense, version 7.0 is not different.
Since the suggested solution here is not what we were looking for, I had to dig in the source a little. I believe I solved the issue and I am posting the solution here so it could help somebody else and/or be implemented in one of the next versions.
Anyway, the main problem is in the method TImageEnVect.GetObjectBoundingBox which for an iekRULER object does not take into consideration the label part but only the line itself.
Also when drawing objects to Bitmaps, the method TImageEnVect.DrawObject effectively creates a clipping rectangle by calling CreateROICanvas based on the rectangle, returned by GetObjectBoundingBox.
I solved this issue by disabling the creation of the "clipping" rectangle for rulers by changing the line
if copyingBack then to if copyingBack and (aobj.Kind <> iekRULER) then
I understand that the ideal solution would be to fix the TImageEnVect.GetObjectBoundingBox method, but the given modification works for all my tests.