Is it meaningful to define a typical gap distance (between edges involved in a gap), and testing if a distance from an edge to nearest edge is bigger than 0+tolerance but lesser than the “typical” gap distance, then those edges could be highlighted?
If so, then there’s a case which is close to this case (although dealing with open surfaces instead) which could be adapted to this case:
Adapting it to “Orphaned PolySurfaces” should be possible, and even if sometimes giving false positives, it’s only about indicating about candidates for fixing, so indication doesn’t have to be perfect (it would tend to indicate too many cases)
// Rolf