hdiutil: create failed - Operation timed out

I am trying to create a Backup.dmg disk image in a folder on an SMB file system. 1. Using Disk Utility 2. Using hdiutil - hdiutil create -size 4t -fs APFS -volname backup Backup.dmg Both operations start, but after a few minutes, they always fail with create failed - Operation timed out It fails the same way when trying to create an image on a USB-attached disk drive. I recall doing this over a year ago on the same Windows box and sharing SMB folders with no problems. Chat GPT has many options but nothing useful. Google search shows other people with the same problem but not many good solutions. Does anyone have any insight into what is going on here? ---------- *Getting some more insight here from Carbon Copy Cloner...* Some SMB volumes can't support macOS sparse disk images We have received several reports that macOS is unable to create disk images on SMB volumes hosted by various NAS devices. If you attempt to create the disk image in Disk Utility (for example), Disk Utility reports an "RPC Error". After months of investigation, we have concluded that macOS Catalina has more stringent requirements for sparse disk images than previous OSes. Solution: Several users have reported that adjusting the SMB configuration on the NAS to support Time Machine can resolve the problem. Time Machine also uses sparse disk images on NAS volumes, so its requirements for the NAS file sharing service would be the same as those required for generic sparse disk image support. Workaround A: Several users are reporting that connecting to the network volume via AFP rather than SMB resolved the problem: 1. Eject the NAS volume if it's currently mounted 2. Choose "Connect to Server" from the Finder's Go menu 3. Type in "afp://{server address}" to connect to the NAS volume via AFP 4. Choose "New disk image..." from CCC's Destination selector and specify a new disk image on the AFP-mounted NAS volume Workaround B: If connecting to your NAS volume via AFP is not an option, then you can back up user data (e.g. your home folder) directly to the NAS volume (i.e. don't use a disk image). We also recommend disabling support for extended attributes (via the Advanced Settings). ---------- *I still have not solved the issue... still researching...*