When listing all the objects in a S3 bucket, the following WARNING is shown every time:

WARNING: Retrying failed request: /?marker=100PENTX/IMGP0125.JPG ()
WARNING: Waiting 3 sec...

In the end the listing does succeed, but this warning is given every time.
Looks like it's something to do with a failed "next marker" request, the bucket contains more than 1000 files. After initial failure, it always succeeds.