I haven't ever heard anything about DZR15 f/w, but the ZW15R has a beta firmware available that helps with the issue of them dropping off the mesh.
You need to email dssupport@leviton.com and ask them to help enroll you in the 15R beta.
These steps work for both the other f/w files Leviton has publicly available and the 15R beta f/w.
