Triangulation looks odd when triangulating Survey. Ther triangulation ends up with strings zig zagging across the display and anything which is subsequently done with the triangulation is incorrect.
Historically, MX Style sets have designated L strings as spot levels, and then annotated the spot levels using the detailed interpretation in the Style Set. However this has inherent issues, as L strings are just normal 3d strings with string links between them. This then causes anomalies in the triangulation as the analysis takes the string in Point order, thus creating triangulations as those shown above.
To get around the problem, rename to L strings to P Strings. P strings are special Point Strings, and contain no string point links. Each point is discrete in its own right and has no links to other points. The analysis then processes them differently, and creates a true triangulation See Below
If you need to, you can then edit the Style Set being used to display the P strings with Spot Level information.