<p>I think that the answer is in the randomizing part of the algorithm. You can find more details here:</p>

<p><a href="https://github.com/gephi/gephi/wiki/Modularity" rel="nofollow noreferrer">https://github.com/gephi/gephi/wiki/Modularity</a></p>

<p><a href="https://sites.google.com/site/findcommunities/" rel="nofollow noreferrer">https://sites.google.com/site/findcommunities/</a></p>

<p><a href="http://lanl.arxiv.org/abs/0803.0476" rel="nofollow noreferrer">http://lanl.arxiv.org/abs/0803.0476</a></p>
Iterative modularity
<p>I have run modulartiy edge_weight/randomized at a resolution of 1, atleast 20 times on the same network. This is the same network I have created based on the following rule. Two nodes are related if they have atleast one item in common. Every time I run modularity I get a little different node distribution among communities. Additionally, I get 9 or 10 communities but it is never consistent. Any comment or help is much appreciated.</p>