In directx12 mesh shaders example,there is an error.

In MeshletGenerator/Generation.cpp, the meshletize template function.
After you enter the area of AddToMeshlet()==True , you refresh the candidate and remark the scores.
An error occur that there is a situation that is meshlet is not full but the candidate has been empty,(which often occurs in the seed triangle is in the clusters has been clustered), you ignore the situation and run
/*
if (candidates.empty())
{
while (triIndex < triCount && checklist[triIndex])
++triIndex;

        if (triIndex == triCount)
            break;

        candidates.push_back(std::make_pair(triIndex, 0.0f));
        candidateCheck.insert(triIndex);
    }

*/
so that the meshlet was added with a new seed triangle which is not adjcent to the meshlet.

so you have to change that line /* if (IsMeshletFull(maxVerts, maxPrims, *curr)) */
into if (IsMeshletFull(maxVerts, maxPrims, *curr)||candidate.empty())

Read MeshletGenerator/Generation.cpp and the meshletize template function first. Trace the AddToMeshlet() path where candidates are refreshed and inspect the existing candidate-empty handling. Done means the reported non-full meshlet and empty-candidate case closes the meshlet without selecting a non-adjacent seed, while the DirectX 12 mesh shaders example still works.