The NVRAM error message and the VLAN config loss are two separate issues and not related.
- For the NVRAM error message, the reboot repairs the chains in the file system. As mentioned by the customer, the NVRAM error has no impact on functionality, just for saving the config from ramdisk to NVRAM. Basically, any CLI configurations made while the error is seen, will not be present after reboot. A boot fixes this state. Confirmed in LAB and by client.
- The reboot of the stack made visible the VLAN issue, which was already present. The upgrade to 5.12.2 (or 5.12.3) will not fix the VLAN config, but will prevent this loss in a similar scenario. As mentioned before, for these stacks, manual reconfiguration will be needed after the upgrade, so a valid ASCII file must be close at hand.