When Eon Browser, or any BlackPearl client, attempts to transfer files, it first sends a Create Bulk Put command to BlackPearl with the list of file names that it will transfer. Those file names then become reserved in BlackPearl, and no other job/client can upload files with those names. If another job then attempts to upload files with those same names, even if the first job was not successful, the second job will fail with the error message you saw. Delete the files (actually file references/names) in BlackPearl to clear the issue.
Note that this is a completely separate and unrelated issue from the permission error you are receiving.