Does this mean that there is some broken reference in the assembly?
That symbol means the assembly is "Flexible" instead of Rigid.
Go to the properties of the assembly to change this solve as state.
Thanks Mike, Never encountered that before.
This is what the help file said on this.
Flexible Sub assembly
It means your subassembly is Flexible.
RMB->Component Properties: Solve As (Rigid/Flexible)
It means you can have an flexible sub-assembly within a rigid assembly where rotation, linear translation or such that is allowed.
Retrieving data ...