Same issue for me with the RC, in my base trying to reinstall Infuse. I've tried to clear caches, remove all other references, sign-out and back into the App Store and many other things.
Hoping someone might suggest something else.
[PurchaseService]: [9D6B1043] Starting purchase of 1136220934:com.firecore.infuse by com.apple.AppStore
BUY9D6B1043/com.firecore.infuse:1136220934] Starting purchase for client: com.apple.AppStore
[BUY9D6B1043/com.firecore.infuse:1136220934] Failing this request as a duplicate of UPDDE9C96EE/com.firecore.infuse:1136220934
DetectDuplicateRequestTask completing with error: Error Domain=ASDErrorDomain Code=506 "Duplicate request" UserInfo={NSLocalizedDescription=Duplicate request, NSLocalizedFailureReason=Request is a duplicate of UPDDE9C96EE/com.firecore.infuse:1136220934}
[PurchaseService]: [9D6B1043] Purchase completed with error: Error Domain=ASDErrorDomain Code=506 "Duplicate request" UserInfo={NSLocalizedDescription=Duplicate request, NSLocalizedFailureReason=Request is a duplicate of UPDDE9C96EE/com.firecore.infuse:1136220934}
