A domain in it's only right as to be wrong a fair amount of times due to other given TARGETS to define.
Clearly look at bus number 18613.
If you give the BUS as a RIGID DOMAIN as anything a TARGET on that bus can disqualify a RIGID DOMAIN as a DOMAIN in itself on the BUS.
The DOMAIN RANGER 113 116 118 case in point makes the RIGID DOMAIN wrong.