The message from the bot was misleading, from syslog the error was from the USB drive (sdb) not the internal one
--- Mar 2 19:49:48 ubuntu kernel: [ 236.533551] FAT-fs (sdb1): error, fat_get_cluster: invalid cluster chain (i_pos 510340) ---
Could you try with another usb stick or create it again and see if that fixes your problem ?
The message from the bot was misleading, from syslog the error was from the USB drive (sdb) not the internal one
---
Mar 2 19:49:48 ubuntu kernel: [ 236.533551] FAT-fs (sdb1): error, fat_get_cluster: invalid cluster chain (i_pos 510340)
---
Could you try with another usb stick or create it again and see if that fixes your problem ?