I have an ISR4331 router spitting out two error codes. They appear to occur in pairs, although the first one to show up in the logs is the metadata buffers message.
%IOSXE-3-PLATFORM: R0/0: kernel: EXT2-fs (sda1): previous I/O error to superblock detected
%IOSXE-2-PLATFORM: R0/0: kernel: EXT2-fs (sda1): error: ext2_fsync: detected IO error when writing metadata buffers
There doesn't seem to be any specific reference to these messages in the bug searches I've done that pertain to the ISR4300 series or the ISR4000 series devices.
