I'm trying to insert a sub-assembly of a PTO shaft into a larger assembly. In order to properly constrain the PTO the sub-assembly needs to be flexible and able to rotate freely. After switching the sub-assembly from "rigid" to "flexible" in the properties menu, I am able to constrain the PTO as I had hoped. However, if I make any changes to any of the other parts or assemblies (causing a rebuild) I get numerous errors. The source of all these errors being the rebuild of the PTO. Setting the PTO to "rigid" eliminates these errors, but then I can't constrain the sub-assembly. The PTO assembly has no internal errors and rebuilds fine in its own file. Any tips?