New Post: Dissolve causes SelectShapes to give false positives

After I create a (linear) shapefile via Dissolve, SelectShapes correctly selects expected shapes, but also sometimes selects shapes that are not within the selection box/specified extent. FixUpShapes does not help. It seems like the problem should be in the source shapefile, but I have tried the function on multiple shapefiles with the same result.

Many thanks to anyone who can provide assistance.

Don Rahmlow
Readfield, ME
US