I am having a very similar problem. Have tried restarting the Cloak application and locking and unlocking my wallet. Nothing seems to change the failure rate which seems to be about the same the original poster's. The problem has existed since first staking using the Cloak app, about a month. I had thought that this was an issue with internet connectivity as I was using DSL. However I am on cable now with plenty of bandwidth and the problem is still there.
OS: Mac OS 10.12.6
App: CloakCoin v22.214.171.124