My current problem is that on my iPhone I only can access some of some of my speakers and it seems different based on where I am in the house/which mesh node my phone is connected to. To further investigate this problem I've been experimenting with the webapp on my hardwired iMac and with that I can play music on every speaker but only certain speakers can be grouped together.
Before I jump into some details about the issues I'll give you a full picture of my current network setup. Here’s an image of my current setup:

Some notable things are that I've added a wired TP Link TL-R605 router into the setup to allow me to set my Deco mesh system to bridge mode ("acces point mode" per the Deco app). This was necessary as my Nokia ONT has no routing capabilities, for reference my internet provider is Ziply Fiber and they provided the Nokia ONT. After that you can see my full network map, the solid lines are CAT6 ethernet runs and the dashed lines are wireless connections.
In my router settings I have set all of the devices in the diagram to have specified IP addresses permanently. I've also set my iPhone, my wife's iPhone, and my Samsung Windows laptop to have permanent IPs.
As mentioned previously my Deco mesh system is set to access point mode. I've turned on the "IoT Network" setting on the Deco network which creates a 2.4 GhZ network that all my Sonos devices and my iPhones are connected to wirelessly. I do not have any of the Sonos devices connected to ethernet at this point; I'm trying to avoid that because most of my Sonos devices that are Sonosnet compatible are closer to one of my mesh nodes than they are another Sonosnet compatible device. They are set to connect to the nodes shown in the diagram and have "strong" signal strength per the Deco app.
In terms of the issues I'm experiencing I'll start with what's going on with the webapp on my iMac. As mentioned previously I can play apple music to any device in my system individually. The problem is that only certain speakers can be grouped together. I've included a table below that show what speakers are able to be grouped together. To explain the table a little bit when I play music on the Basement Connect I'm able to group that speaker with the Basement Bedroom, Bathroom, Living Room, and Nursery. If I try to include the Garage or Kitchen speakers in the group I get a "Something went wrong" error. The only patterns I've been able to see are that my Garage Roam can only group with the Nursery and the Kitchen can't group with anything. This same matrix proves true when I try and play music via the Sonos Webapp on my Samsung Windows laptop connected to my 4 GhZ wiFI network.

On my phone the problems occur with both the Sonos App and AirPlay. Depending on where I am in the house I can play to different speakers via the Sonos App and AirPlay. I think this is tied to which mesh node my phone is connected to but I can't prove that. For the life of me I haven't been able to get my phone to connect straight to the Main Basement node but here’s a table with what my connectivity looks like on the other nodes via the app and AirPlay.

To explain this table when my phone is connected to the Kitchen X50 mesh node I can only play music on the Kitchen One speaker via the Sonos App or AirPlay. In this instance on the Sonos App only the Kitchen One is shown as part of my system or an option to play to.
However when my phone connects to the Garage node I can play to the Basement, Garage, and Nursery via the app, and the Garage and Nursery via AirPlay. This is consistent as the Connect is not AirPlay compatible. I'll update with further experimentation and info. Any ideas?