Modifying evelation heights of line string contours

I am currently working with Microstation v8 xm and i have a data set with 3d contours. the contours have been converted to line string (as per spec) i have noticed that the elevation of each edited contour, either by extending line, inserting vertices or even moving the contour to another position will change its elevation height to +/-10000m. My worksheet is set at a rotation view of 45deg, but surly this can only affect xy not z direction. I am able to edit the elevation depth using the info tool but this just seems to affect the position of the contour rather than the height. When i view my worksheet in the isometric view (45deg sideview) you can see the elevation spikes of my dataset. Also, working on top view seems to have this problem too. One method is to export the contours as .dwg format and amending the elevation using terramodel, but surely there should be some other way to edit contour heights without affecting their position?

Any help would be greatly appreciated.