If you’re using macOS 14 or 15 and ask DropDMG to create a disk image from a file that’s locked or a folder containing locked files, DropDMG may report the error:
hdiutil: create failed - Operation not permitted. DropDMG does not have sufficient file permissions.
even though DropDMG does have the proper file permissions. This is caused by a macOS bug (FB15923924). You can work around it by clicking this link, which will tell DropDMG to use a different code path that avoids the bug. (Essentially, DropDMG will copy the files itself instead of relying on macOS’s disk imaging subsystem to do that.) The workaround can be disabled by clicking this link.