UPDATE: I was able to create a project that duplicates the problem [attached]. GeometryEngine at 100.2 has a problem which 10.2.7 doesn't have. I have two different geometries with the same spatial reference, yet hydrated from different sources (one from the map, one from a feature layer). If I try to to perform an operation such as Contains or Disjoint, I get the error "Value does not fall within the expected range". If I project one geometry to the other's SR then the operation works fine. The SR is defined by a WkText, and the WkText of both SRs is identical. Has anyone else seen this?