I’m pretty sure my Z-wave mesh is fine.
All I own are Z-wave Plus smart switches and dimmers. I have mostly Zooz but also a couple of Levitons and a couple of GEs. All of them use the stock DTHs and show as local. I only use Smart Lighting and new app Scenes, no WebCore.
All but three of my devices are in one room. The heart of the house is a single open room that incorporates kitchen, dining room, wet bar, and living room. The front entrance, three hallways, and three sliding glass doors open off this room. With ceiling can lights, hanging fixtures, counter lights, lighted cabinets and most of the exterior lights, there are over 30 Decora switches around the perimeter of this one room.
All but four of my Z-wave Plus devices are in this room. One of the four not in this room has to route thru this room to reach the hub.
When I do a Z-wave repair, everything in this room plus the one that routes thru it throws errors, usually “cannot update neighbors” or something like that. There’s a long, rambling topic I started about this last winter.
All my devices work. I just get random 2 to 15 second delays, usually when triggering multiple devices via a scene. Different devices in the same multi-gang box can be switch instantly or have delays.