I have been on a number of customer calls recently where people were hitting problems for which we have already released hot-fixes. If you are running a Windows Server 2012 R2 Hyper-V cluster I would strongly recommend that you read this article:
Recommended hotfixes and updates for Windows Server 2012 R2-based failover clusters
This article lists a number of hotfixes that are good for any Windows Server 2012 R2 cluster as well as some that are specific to Windows Server 2012 R2 Hyper-V clusters. It also discusses what each issue is, and how it has been addressed.