I had recently had this issue and fixed on one file server but now I am seeing the same issue on another. I have switched my group policy drive maps to Update rather than replace.
I have multiple users running Windows 8.1 and Outlook 2013 32bit. We use cached-exchange mode and each user has a series of PST files stored on a network share.
I am seeing a number of mrxsmb 50 warnings in the event logs, and the end user's Outlook crashes when these events happen.
This is strictly an issue with Outlook 2013 and Windows 8.1, Clients using Windows 7 and Outlook 2013 are fine, as well as clients running Windows 8.1 with Outlook 2007.