I had the same issue. I resolved it by following what was discovered here: EX2 and Amazon S3 backup failure and versioning - #6 by JOSH_LOOMIS
Basically what WD call “Incremental” actually means “Full Backup”.
The option you want is “Overwrite Existing File(s)”. This will upload new or changed files and skip the existing ones.
Crazy, I know. I can only conclude that either WD’s understanding of the word “Incremental” is different from their users, or they made a mistake when developing their firmware.
