I initially struggled with the same “symptoms” you describe. Unfortunately this was at a second home 2000 miles away. I realized after I got home that I did not understand mesh networks, and smarthings methods to repair/heal these networks.
Anyway, second trip to the home I added more than another half dozen or more “repeaters” - mainly iris 3210-L’s (with both zwave and zigbee repeaters). I also thoroughly replotted the placement of all the repeaters, and performed MANY zwave network repairs until it passed without errors. Similarly I “healed” the zigbee mesh multiple times.
I now have zero drop outs.
I would invest some time and learn how to layout, and implement an stronger mesh network. A quick glance at your devices and it seems you may be lacking repeaters for your size residence.
Wifi can also interfere with the mesh. there is a ton of info around to help troubleshoot your problems. Are you using wifi with your v3 hub? If yes, check the wifi channel in your IDE for your hub and make sure your router channel is not overlapping. Also, check if your neighbors wifi might be an issue.
Start with tguac’s wiki - it is extremely helpful.