N2048 stack firmware update error

I have 27 Dell N2048 switches in the network and recently upgraded the firmware on one stack in response to a memory leak error.  That switch lost all the configuration on the second member of the stack. Once may be a fluke, but this has occurred on a second stack as well. I have never had a issue upgrading firmware before but am now reluctant to upgrade any more stacks. Has anyone else experienced this problem?

Previous version:6.1.2.4

Current version 6.2.1.6