You would probably need his template, mapping, etc
Based on the error alone, he’s got a blank field that probably is not validated in the UI so it doesn’t set properly when it’s iterating the build. In the back end there’s no isset check which could be in any number of places.
So after More Digging, if I switch the phone type from vvx 311 to vvx 310 ( in the extension mapping) . and i don’t use the UCP Custom enterys to do the save and rebuild. it works fine. the UCP will not rebuild the files in the tftpboot folder and the VVX 311 will not recognize vvx color Sidecar.