It seems that a number of editors are finding that they sometimes have elevation level nulled out after saving, on segments that had previously been saved with valid elevation data. Not only is it affecting segments that have been edited, it is affecting multiple segments off the same junction.

See start of discussion here and here

Editors reporting the phenomenon so far: ctpoole, atomicdecay, qwaletee, rgatland, orbitc.

Several other editors cannot reproduce the problem.

My detailed summary of the actions I took that produced the error:
Changing a junction, or maybe the elevation of one segment attached to the junction, seems to drop elevation from all the segments in the junction. This appears to be true even if I select the unexpectedly modified segments -- the standard WME segment properties show blank elevation.

If I have a segment that has directional or reverse connection issues and fix it, after I save, it gets highlighted for elevation out of range, but it wasn't highlighted for that before. (I.e., when I select the segment, it only shows the reverse connection problem, it does not also show an elevation note.) This may simply be a symptom of the above -- until I changed the junction to eliminate the reverse connection, perhaps the segment had a properly assigned elevation, so there was no reason to show an elevation note. Once I saved, and the elevation was lost, then there was a reason to display the issue.

So I'm going to vote for there being a problem with WME killing elevation values right now, or a problem with JNF/toolbox doing it.