(Google to Google) Error 404: File not found

I have two separate scenarios involving a total of four remotes, two source and two target. When I opened this issue, I could reproduce the problem reported here in both scenarios, one of which is the data included in this topic.

In both scenarios I can run lsf with the --drive-shared-with-me option on the target and see the files in the source that I want moved. Does that not rule out a permissions issue? The answer you linked to refers to upgrading Content Manager access to Manager, but that is for Team Drives, which is not part of my scenario. I am dealing strictly with My Drives.

What I have found since opening this issue is that for one of the scenarios--two different remotes named Source: and Target:--the problem is resolved by adding --drive-root-folder-id "root". I don't know why, but it appears Rclone cannot access files at the root of My Drive without that option set. Any background information to explain that is appreciated.

For the other scenario, I now get a different error when passing in --drive-root-folder-id "root".

λ rclone move SourceBR: TargetBR: --drive-server-side-across-configs --drive-root-folder-id "root" -vv
2021/01/22 09:58:01 DEBUG : rclone: Version "v1.53.3" starting with parameters ["rclone" "move" "SourceBR:" "TargetBR:" "--drive-server-side-across-configs" "--drive-root-folder-id" "root" "-vv"]
2021/01/22 09:58:01 DEBUG : Using config file from "C:\\Users\\Chad\\.config\\rclone\\rclone.conf"
2021/01/22 09:58:01 DEBUG : Creating backend with remote "SourceBR:"
2021/01/22 09:58:01 DEBUG : Creating backend with remote "TargetBR:"
2021/01/22 09:58:02 ERROR : Copy of Round2 Doc.docx: Couldn't move: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:02 DEBUG : Google drive root '': Waiting for checks to finish
2021/01/22 09:58:02 DEBUG : Google drive root '': Waiting for transfers to finish
2021/01/22 09:58:02 INFO  : Round2 Doc.docx: Moved (server side)
2021/01/22 09:58:03 INFO  : Copy2 of Top 5 Analysis.pptx: Moved (server side)
2021/01/22 09:58:03 INFO  : There was nothing to transfer
2021/01/22 09:58:03 ERROR : Attempt 1/3 failed with 1 errors and: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:03 DEBUG : Google drive root '': Waiting for checks to finish
2021/01/22 09:58:03 DEBUG : Google drive root '': Waiting for transfers to finish
2021/01/22 09:58:03 ERROR : Copy of Round2 Doc.docx: Couldn't move: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:03 INFO  : Round2 Doc.docx: Moved (server side)
2021/01/22 09:58:04 INFO  : Copy2 of Top 5 Analysis.pptx: Moved (server side)
2021/01/22 09:58:04 INFO  : There was nothing to transfer
2021/01/22 09:58:04 ERROR : Attempt 2/3 failed with 1 errors and: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:04 DEBUG : Google drive root '': Waiting for checks to finish
2021/01/22 09:58:04 DEBUG : Google drive root '': Waiting for transfers to finish
2021/01/22 09:58:04 ERROR : Copy of Round2 Doc.docx: Couldn't move: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:04 INFO  : Round2 Doc.docx: Moved (server side)
2021/01/22 09:58:04 INFO  : Copy2 of Top 5 Analysis.pptx: Moved (server side)
2021/01/22 09:58:04 INFO  : There was nothing to transfer
2021/01/22 09:58:04 ERROR : Attempt 3/3 failed with 1 errors and: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions
2021/01/22 09:58:04 INFO  :
Transferred:             0 / 0 Bytes, -, 0 Bytes/s, ETA -
Errors:                 1 (retrying may help)
Checks:                 9 / 9, 100%
Renamed:                6
Elapsed time:         3.4s

2021/01/22 09:58:04 DEBUG : 16 go routines active
2021/01/22 09:58:04 Failed to move: googleapi: Error 403: The user does not have sufficient permissions for this file., insufficientFilePermissions

λ rclone lsf TargetBR:
Copy of Top 5 Analysis.pptx
SheetOStuff.xlsx
subdir/

Note that even though there's an indication in the logging that the files were moved, they were not. I understand that HTTP 403 again points to permissions, but I am still left wondering why I can see the files in the source that I want moved. Any idea how I can determine exactly what permissions are needed but are lacking? The impersonation user in TargetBR: has Editor access to the files in SourceBR:, and that is the maximum level of access I can provide.