RN-316 - Corrupt Files.

Two 316 ReadyNAS boxes.
One Producrion, One Backup.
Same firmware: 6.10.2
Prod box has WD Red Pro 6 6TB drives.
Backup Box has WD Red 6TB drvies (Not Pro)

Both boxes used for media files.

Prod box is missing FLAC files. When I open a file with MP3tag the file (song) shows as a FLAC file with no tag (only filename). It will not play. Foobar gives this message:

Unable to open item for playback (Unsupported format or corrupted file):
"\\316-prod\db-prod\DB-BLs\Beach Boys\- Goodbye Surfing Hello God - CD 1.5\01 - Hi We're The Beach Boys - Beach Boys.flac"

There is no file there but the 316 Production box thinks there is. It shows as a file.

Same file play fine on the Backup box.

I'm going to call these unplayable files "ghost" files.

My first step was to delete the ghost files from the 316 Production box and restore the same file from the Backup box. The copy works fine BUT the file now on the Production box doesn't necessarily play. It's another ghost file. Some play, some do not.

The MAIN share is Music. In Music there are 10 sub-shares by category. In the sub-share I'm working there are 40 sub-shares (Artist). In all there are 9500 files (songs).

Of those 9500 there are 154 ghost files.

There are no log file alert messages. The system indicates it's healhty. BUT when I select Diagnotics on Raidar I get this message: 

Successfully completed diagnostics
System
No errors found.
Logs
2020-01-23 18:46:01: raidard[2978]: segfault at 7ffedc880000 ip 0000000000401d20 sp 00007ffedc87dab8 error 4 in raidard[400000+6000]

I'm stumped. Is this a drive error or memory area? Searching online gives an answer whic is above my pay grade. Why doesn't the system place a message in the log file area?

Questions:

How do I determine what the real issue is? (Bad disks? How do I know? Can I fix?)
What's the best way to attack this issue? (I'll assume a full restore from Backup but I MUST solve the issue first?)
Finally, what should I NOT do?

Dave-