Timing (??) error in ModifyContour triangulation=1

I created a wave tripletWave[n][3] that holds x-y-z triplets for creating a (2D) Delaunay triangulation, then created the the triangulation using "ModifyContour triangulation=1". I then plotted it in a graph. The triangulation occurs automatically; if I delete a row from tripletWave, the triangulation in my graph immediately updates, which is very convenient.

Also, I can extract a list of triangle vertices used in the current triangulation, as well as two waves containing the x-y points that represent the vertices of the triangles. These latter waves should match the x-y columns of triangleWave, which they do but not exactly—they're off in the 3rd or 4th decimal place for some reason (this is not an issue for me).

My program appears to have some kind of timing error which is hard to pin down. To illustrate this, I have created a MNWE (minimal non-working example):

function test()
 
    Variable Nt, Nxy
    Wave tripletWave        // (n x 3) wave of x-y-z triplets
    
    DeletePoints 35,1, tripletWave // Delete one row
    
    WMDuplicateTraceWave("Graph0","tripletWave=xymarkers")  // Extracts triangulation waves
    
    Wave px = 'tripletWave=xymarkers.x'  // This is one of the waves extracted. Should have same # of points as tripletWave
    
    Nt = DimSize(tripletWave,0)
    Nxy = numpnts(px)
    
    print "tripletWave size = ", Nt
    print "xymarkers size = ", Nxy
 
end

This function does the following. First, it deletes a row from the original tripletWave. Then, it uses the function "WMDuplicateTraceWave" from "Extract Contours As Waves.ipf," to extract the wave hidden in tripletWave that contains the same (almost) values as in tripletWave. Then it finds the number of points in tripletWave and the extracted copy, "tripletWave=xymarkers.x". These two sizes are not the same.  tripletWave is always one smaller than tripletWave=xymarkers.x. In other words, the function correctly deletes the row from tripletWave, but does not delete it from  "tripletWave=xymarkers.x".

The reason that this seems to be some sort of timing or overrun error is that if I type in each of the commands into the command line and execute them one at a time, the two sizes match and an inspection of "tripletWave=xymarkers.x" shows that the correct row has been deleted. Further, if I run the function in the debugger, stepping line-by-line, it works as well.

My interpretation is that when a point is deleted from tripletWave, a rather lengthy (in time) background task needs to run to update the Delaunay triangulation. But before this can finish (I presume) I start the WMDuplicateTraceWave extraction, which returns the original internal version from which the row has not yet been deleted. If I run line-by-line there is plenty of time for the triangulation to complete.

Is my interpretation correct? But more importantly, how should I handle this case? I would like to delete a row from tripletWave and then extract the correctly updated wave using WMDuplicateTraceWave, and have the two waves match in length and content.

Sorry for the very long post!