The add-on is able to process almost all kinds of UV topologies, even if they are really bad (e.g. faces with self-intersecting edges, many doubled vertices, etc.). However, in very rare cases, due to floating point precision errors, topology of some UV islands cannot be analyzed properly. In such a situation, the add-on will return Invalid Topology error and select all problematic UV islands. You have two options to solve this kind of a problem:
- fix the topology of the islands (unwrap the islands properly so they do not have doubled vertices, self-intersecting edges). This is the recommended way forward,
- 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.