Thanks Tomek and Dan. Definitely issues with this input data that will impact the analysis results that need taking care of. Bad data in, bad data out.
Once I repair all the issues... spatial reference, bad geometries... it appears to work as it should.
Spatial Reference set incorrectly:
Checking Spatial Reference...
XYTOLERANCE ISSUE - NOT set to default. Current: 1.9384789092521745e-05 | Default for this SR: 0.001
XYRESOLUTION ISSUE - NOT set to default. Current: 2.423098636565218e-06 | Default for this SR: 0.0001
And as mentioned lots of geometry issues:
(300+ bad geometries reported)
Thx. Ken