Previously I did the antenna mod on my C7 (just for the Z-wave antenna) and the mesh eventually showed directs to all my devices but 1.
I jumped on the C8 model for the newer chips and did a migration which went pretty smooth.
However the mesh only has 25 of of the 38 devices showing direct. I have tried using the large antenna that was suggested in the C7 antenna mod thread that I had on my C7 hub with no improvement. I have also tried moving it about the room.
My antennas are all pointed vertical.
In all cases I have waited a few days to see how the mesh is settling before tweaking again.
I'm in the same boat. I've got a C7 with antenna mod and just ordered a C8. I'm hoping there is some improvement or else I may have wasted $150. I will be running tests with both using several antennas to see if that makes any difference.
I do know from experience (at least on the 700 chip) that it takes the mesh 5-10 days to settle down.
I'd give it some time to settle, and adjust connections and routes. Mine changed over time. I did try to "help" a little some some odd routings by doing individual device repairs, but tried my best to leave it alone. In the end, if everything is working normally, what you see on the Z-Wave Details page really isn't a concern.
We have had some automations and voice controls where some of the devices have failed and require another ping so to speak. So I am hoping it will settle out.
If you haven't done a shut down/pull power/wait 1 minute/plug in again, that can help in some cases w/missing routes after a boot-up. You can try that, won't hurt, might help.