Bad master directory block error (shutdown cause -60) and random restarts without other symptoms

Folks,

On my 8 year-old 2010 MacBook Pro, I started getting a bunch of random shutdowns starting about a week ago. I reinstalled High Sierra after the first few, but I'm still getting them. Terminal reported the shutdown code -60 in all cases, which I understand is due to a bad master directory block.

However, I'm having none of the symptoms described in this post - the only thing going wrong with my computer is that it shuts down at random and unpredictable intervals (~1x a day). I sometimes get the kernel panic message, and sometimes I don't. Disk utility can find nothing wrong with my drive. As mentioned, I reinstalled the OS, and I ran disk utility after wiping the hard drive, plus I ran it after the most recent incident. The drive is a Samsung SSD that I self-installed about 5 years ago. I only just started getting these shutdowns. No issues with the drive that I can detect.

I'll note that my battery is extremely well-worn, but I basically keep the MBP plugged in nearly full-time, and all the incidents happened on AC power.

Any thoughts as to why this might be happening?

Results from running Disk Utility after the last shutdown are:

dev/rdisk1s1: 
/dev/rdisk1s1: fsck_apfs started at Thu May 17 17:28:43 2018
/dev/rdisk1s1: ** Checking volume.
/dev/rdisk1s1: ** Checking the container superblock.
/dev/rdisk1s1: ** Checking the EFI jumpstart record.
/dev/rdisk1s1: ** Checking the space manager.
/dev/rdisk1s1: ** Checking the object map.
/dev/rdisk1s1: ** Checking the APFS volume superblock.
/dev/rdisk1s1: ** Checking the object map.
/dev/rdisk1s1: ** Checking the fsroot tree.
/dev/rdisk1s1: ** Checking the snapshot metadata tree.
/dev/rdisk1s1: ** Checking the extent ref tree.
/dev/rdisk1s1: ** Checking the snapshots.
/dev/rdisk1s1: ** Checking snapshot 1 of 9.
/dev/rdisk1s1: ** Checking snapshot 2 of 9.
/dev/rdisk1s1: ** Checking snapshot 3 of 9.
/dev/rdisk1s1: ** Checking snapshot 4 of 9.
/dev/rdisk1s1: ** Checking snapshot 5 of 9.
/dev/rdisk1s1: ** Checking snapshot 6 of 9.
/dev/rdisk1s1: ** Checking snapshot 7 of 9.
/dev/rdisk1s1: ** Checking snapshot 8 of 9.
/dev/rdisk1s1: ** Checking snapshot 9 of 9.
/dev/rdisk1s1: ** Verifying allocated space.
/dev/rdisk1s1: ** The volume /dev/rdisk1s1 appears to be OK.
/dev/rdisk1s1: fsck_apfs completed at Thu May 17 17:30:45 2018
/dev/rdisk1s1: 

@Allan suggested that the symptoms I reported were consistent with a failing SATA cable, which is a known issue. He suggested that I check the disk status with some utilities. I could find no disk issues when I did this.

The post I linked to earlier suggested resetting the SMC in addition to checking for disk errors. I reset the SMC. I have not experienced any unexplained shutdowns since. Any further errors, and I'll investigate that SATA cable.