Practical use of Mesh Description in Blueprint

Alright, I’ve made significant advances in understanding the MeshDescrption and related classes. However, I am now facing a very annoying problem that I have no idea how to solve - maybe I lack enough understanding in the finer aspects of UE, but I have absolutely no idea why this error happens when I call the test Generate function I’ve created:

I invoke this from Blueprint, but the code is entirely in C++ and it compiles without any issues. The error is actually reproducible in different places in that function code, which are essentially different in nature (exception where the arrow points):

TArray<FVertexInstanceID> VertexInstanceIds;
VertexInstanceIds.SetNum( 12 );
// creating the vertices and other necessary stuff here in between...
-> MeshDescriptionBuilder.AppendTriangle( VertexInstanceIds[2], VertexInstanceIds[1], VertexInstanceIds[0], PolygonGroup );

and here:

FStaticMeshConstAttributes MeshDescriptionAttributes( MeshDescription );
-> TVertexAttributesConstRef<FVector3f> VertexPositions = MeshDescriptionAttributes.GetVertexPositions();

So, I am thinking it might be an issue with all these additional modules linking, however, I do have them all in the build.cs file. I’ve been trying to get this to work for a while now, but with no success. Any guidance or help will be much appreciated.

Edit: Of course, I debugged it. The objects and arrays are all looking fine and there are no null elements that could be causing this access violation. The Evaluation tool, however, has the same difficulties evaluating these expressions, but the inspection of the variables works without any problem (i.e. I can see the elements in the arrays and objects have these methods available at runtime).