Did anyone notice that masternode wallet shows more coins than it should over time? If you restart you'll see half of the amount earned that was shown before.
I have the same problem - during sync with the blockchain wallet may register double rewards while amount is showing correct in the Transactions page. You cannot spend "extra" rewards - it will result in the "conflicted" transaction.
Restarting the wallet fixes to the correct amount. It should be a minor bug - hope it's not difficult to fix it.