The $expand query is not valid for field 'Author'
This message shows up in 2 different situations. Pick the one that matches yours:
- A copy job reports "finished" before the target shows every file – verify after the target settles, and read authors with $expandAfter CreateCopyJobs reports JobState 0, the target's /items can still miss hundreds of files for a while; re-read until two reads match, and compare authors via $expand on /items, not siteusersCause and fix →
- CreateCopyJobs: the library root is refused, progress logs are handed out once, and JobWarning is not a failurePassing a document library's root folder URL to CreateCopyJobs fails with HTTP 500 "Null value for source item" while a subfolder URL copies the folder with its content; several file names containing the hash sign break a multi-URI job with HTTP 400 unless it is sent as %23; GetCopyJobProgress returns only the log entries queued since the previous call, a job emits several JobStart/JobEnd pairs so JobEnd alone is not completion (JobState 0 is), a successful copy can carry a JobWarning about label based policy, ListItemAllFields refuses $expand=Author, and item-level unique permissions are not copied (IncludeItemPermissions fails with HTTP 500 on a copy) but can be re-applied afterwards without touching Modified, every job must take URIs from one parent folder into a destination that already exists, and NameConflictBehavior 0 silently skips an existing file when the same job also carries a new one, so the conflict count must come from the destination, not from the logCause and fix →