Z-Wave Range Getting Worse with More Dimmers

I am using a Hubitat C7 with 2.2.6.139 and Inovelli Red Dimmers (“RD”), Black Switches and the Fan+Lights.

As a test I started with 3 RDs back in February. 1 is in the hall right outside the room where my hub is and the other 2 (for the kitchen and dinning room) are down a hall and around the corner from the hub. All 3 got a green light when I added them and there were no problems. They all continue to work with the Hubitat Button Controller rules I created for them. The kitchen and dinning room RDs are in the same 2 gang box.

I was able to exclude/include the kitchen dimmer to remove security. But, I was unable to exclude the dinning room, even with hub reboots (which is another story). So, just for the heck of it I did the range test and the dinning room dimmer is now failing (LED turns red right after a 5 second hold of button C (the config button) has turned green. The kitchen light continues to be green. While literally in the same box, the dinning room one is actually the one closer to hub.

Since originally adding those 3 I’ve added 6 other dimmers (4 RDs and 2 fan+lights) between the hub and the kitchen/dinning room gang box, so the mesh should be stronger not weaker.

Likewise I can’t exclude an Inovelli Black Switch and I’m getting a fail on the range test on it as well even though it closer to the hub, passed the range test when originally included and has a RD in the same gang box that passes the range test, but is on the far side of the hub.

Any ideas of why this is happening? Other than to get a freaking long RJ45 network cord to physically bring the hub closer what can I do?