Hello Dante
The CLI output that you shared seems to be at odds with the given affinity and mask you’ve configured. Given the affinity and mask values, the path via R42 is the expected path that should be selected, but your output shows it taking the path via R39.
What do you see in the output of the show mpls traffic-eng Tunnels command? What do you see in the Explicit Route as shown under the RSVP Path Info and the Shortest Unconstrained Path Info? Take a look at the lesson in the verification sections to see how those outputs tell us about how the tunnel is formed, and see if you can determine the path of the tunnel from that output.
Also, you may want to issue other related commands of the show mpls traffic-eng topology series that will show additional information. You can find these options and what they do at the following Cisco command line reference:
Let us know if these tools have further helped you to investigate and determine the reason behind the unexpected behavior.
I hope this has been helpful!
Laz