Bug#1078423: GRUB randomly breaks and no more boots

[программист некто]

Package: grub-pc
Version: 2.12-5
Severity: grave

Hello. Since version 2.06-8, when #1021846 has been fixed, GRUB may
randomly break and fail to boot. When GRUB is broken, it no more boot,
reboot don't help.

"error: unknown filesystem"
"GRUB rescue:"

The frequency of breakdowns is various. May be 10 normal boots, 1 fail.
3 normal boot, 1 fail.

I found, that one thing may cause failure in next boot with high
probability: delete logs
$ cd /var/log
$ sudo rm syslog daemon.log messages debug
$ sudo reboot

To fix the GRUB I boot from LiveCD and simply type in console:
# mount /dev/sda1 /mnt
# umount /mnt
# reboot

I also used fsck.f2fs, but it usually don't find errors.

$ sudo fdisk --list-details
Disk /dev/sda: 29.82 GiB, 32017047552 bytes, 62533296 sectors
Disk model: TS32GSSD370S    
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc7177f7e

Device     Boot    Start      End  Sectors Id Type
Start-C/H/S  End-C/H/S Attrs /dev/sda1           2048 22763519 22761472
83 Linux                 4/4/1 1023/254/2 /dev/sda2  *    29679616
62531583 32851968  7 HPFS/NTFS/exFAT  1023/254/2 1023/254/2    80

$ disktype /dev/sda1
--- /dev/sda1
Block device, size 10.85 GiB (11653873664 bytes)
F2FS file system (version 1.14)