Tomas Slancik

Karma Ray Import (Vector3 ray:hitP) -> MtlX Transform Point (fromspace: world, tospace: object)

2 issues

1. your group is a primitive group instead of point group
2. you specified it as Source Group in Copy while you want to specify it in Target Group field

if it's easier you don't have to have everything in one stream even though the 3 wire nodes may suggest such workflow
you can isolate pieces you want to constrain, use any of mentioned nodes to create any constraint links you want, potentially convert using RBD Convert Constraints, then just continue with middle output, configure them using RBD Constraint Properties and merge with other constraints

you can also create them in any way you want as each constraint is just a 2 point polyline with s@name of the piece on each point, then you can use RBD Constraint Properties to configure type of constraint
or further customize using other attributes [www.sidefx.com]