Extreme Networks has recently discovered an issue on certain versions of ERS 4800, ERS 4900, and ERS 5900 software which can result in an excessive write frequency to the NVR Flash partitions storing the configuration data on non-base units in stack configurations. This leads to potential early failure of the flash memory component. Once the flash component fails, configuration changes can no longer be saved and upgrading to newer software cannot correct the situation. Once this occurs, the unit will need to be replaced.
The good news is that there is a software fix available.
For more information, please reference the full text of the Field Notice: FN-2018-421 - ERS Flash Failure due to Excessive Writes
The Extreme Networks Quality and Services Teams