The add-on is able to process almost all kind of UV topology, even if it is really bad (e.g. faces with self-intersecting edges, many doubled vertices etc). In very rare cases however, due to floating point precision errors, topology of some UV islands cannot be analyzed properly. In such situation the add-on will return Invalid Topology error and select all problematic UV islands. You have two options to solve this kind of problem:

  • fix the topology of the islands (unwrap the islands properly so they do not have doubled vertices, self-intersecting edges). It is the recommended way,
  • try to apply a simple transformation to the islands and check whether the Invalid Topology error disappears. This method works because topology issues are caused by floating point precision errors. A transformation will change UV coordinates and the outcome of floating point operations may be different. A simple transformation can be: rotating by 90 degrees, scaling by 1.01, moving the islands to a different place.