Maybe this will help?
first thing you need to do is download the two programs above. The free version of Decipher Backup Repair and then iBackupBot.
After installing both of these open up Decipher Backup Repair and choose your corrupted backup and click Repair. After the "repair" finishes go back to the list of available backups and find on the newly "repaired" backup where it says Advanced Repairs. Let the program run once more. After it is done it should provide a list of corrupt files and where they are located. DO NOT HIT NEXT!! THIS WILL REQUIRE YOU TO PURCHASE A LICENSE TO CONTINUE! Keep this window open to the list of corrupted files.
Now open iBackupBot and from the list of backups pick the ORIGINAL backup before doing any sort of "repairs" to it. After selecting on it click system files and just search for the files that are corrupt. After finding them then delete it.
For example a corrupt file of mine was KeyboardDomain Library/Keyboard/Lexierra_ja_JP-dynamic-text.dat
So i searched for Lexierra_ja_JP-dynamic-text.dat. I then deleted it and all other files that were corrupt.
Lastly open iTunes and choose Restore from backup and select the backup you just did all the work on and restore.