Very nice simulation, very interesting to play around with.

I think in your function createPosition one line should be changed to

DeleteDuplicates[
           Join[positions, 
            Select[Round@RandomPoint[region, n - Length[positions]], 
             memberq]]];

in stead of

DeleteDuplicates[
           Join[positions, 
            Select[Round@RandomPoint[region, 200 - Length[positions]], 
             memberq]]];

Very nice simulation, very interesting to play around with.

I think in your function createPosition one line should be changed to

DeleteDuplicates[
           Join[positions, 
            Select[Round@RandomPoint[region, n - Length[positions]], 
             memberq]]];

in stead of

DeleteDuplicates[
           Join[positions, 
            Select[Round@RandomPoint[region, 200 - Length[positions]], 
             memberq]]];

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