Buster System hangs, requires hard reboot

[Ralph Katz <ralph@ralphkatz.com>]

Hi -- Please help me diagnose and fix this problem.

My five month old Dell laptop with updated firmware and new up-to-date
Buster completely hangs and requires a hard reboot after 7-40 days
uptime.  While reading something onscreen or away from the laptop, the
system hangs completely: screen freezes, keyboard is unresponsive, lid
close fails to sleep, can't ssh in, pings fail.  Hard reboot is required.

Actions taken:

- re-installed Buster twice over several months
- ran fsck.ext4 -y /dev/sda2  when fsck failed on boot
- ran bad blocks
- run smartmontools long test weekly; no errors reported in logs.

Sometimes there are errors in syslog like this before a crash:

> Apr  2 06:04:18 spike3 kernel: [539637.882916] EXT4-fs error (device sda2): ext4_lookup:1590: inode #55838123: comm updatedb.mlocat: iget: checksum invalid

Today there were no syslog errors for weeks before the system hung.
After rebooting, errors like these appeared:

> Apr 20 16:05:57 spike3 kernel: [  887.007328] EXT4-fs error (device sda2): ext4_lookup:1590: inode #55842004: comm GMPThread: iget: checksum invalid
> Apr 20 16:08:53 spike3 kernel: [ 1062.821504] EXT4-fs error (device sda2): ext4_lookup:1590: inode #55842002: comm DOM Worker: iget: checksum invalid

Any ideas?

Thanks in advance!
Ralph