Real or technical artifacts due to errors detected in UMAP following run.flowsom()?

[denvercal1234GitHub]

Hi there,

Thanks for the package.

When I used run.flowsom even with meta.k=20 (automatic meta.k resolved 11 clusters), the cluster UMAP doesn't look "right" -- they clumped together on 1 side of the UMAP, and there two tiny clusters that are so separated from everyone.

Do you think these 2 clusters (6 and 20) are simply artifacts? If so, would you mind suggesting some ways to assess that?

Thank you for your help!

Related to #154.