https://forums.autodesk.com/t5/autocad-forum/autocad-2018-backwards-compatibility/td-p/6998902
AutoCAD 2018 - New File Format
not compatible with Trimble Connect Web
Hello Trimble Connect Team
AutoCAD has a new 2018 DWG format that is not backward compatible.
After my test, this format is not yet supported in Trimble Connect Web and Trimble Connect Mobile (Android). It works on Trimble Connect Desktop.
Is this still being worked on for the future?
According to this entry the format is not yet supported:
3D Model Files
Im Anhang ist ein Beispiel DWG.