[Repost due to errant "solved/best ans." click] - FCLM doesn't analyze all FCP libraries.

I shut down my machine. Disconnected all the other external devices. I even turned my printer off, even though there is no cable to it -- just Wi-Fi. OK. Powered up. I tried 3 different cables on three different ports, two of them on the back of the Mac. Always some libraries not analyzed. On these un-analyzed libraries, the size comes out in KB or even "Zero KB", and the libraries are not that small.

Oh, my main cable is 2m. But I have one that's about a foot long! Both had the problem. It's not the cable. I think it's something screwy in FCLM.

No, I haven't asked OWC. I don't expect they would know anything. Everything else on that drive works fine. Maybe I'll try.

If Arctic W. continues to not help me, maybe I'll erase the drive and restore from backup and hope it works and finishes in a reasonable time. The last time I did a restore with Time Machine (Mojave, not Monterey) it misplaced my Movies and iTunes folders and I think even scrambled them a bit. Yeah, that was fun. But why would erasing and restoring the drive help? Only FCLM has a problem with it.

Here is the disk run of HD2.

Mac HD2 first aid on disk

Running First Aid on “OWC Envoy Pro USB-C Media” (disk6)

Checking prerequisites

Checking the partition list

Checking the partition map size

Checking for an EFI system partition

Checking the EFI system partition’s size

Checking the EFI system partition’s file system

Problems were found with the partition map which might prevent booting

The partition map needs to be repaired because there’s a problem with the EFI system partition’s file system. : (-69766)

Operation failed…

The other disk that doesn't work, LaCie 4TB, comes up clean:

Running First Aid on “LaCie 4TB” (disk6s2)

Checking file system and repairing if necessary and if possible.

Volume was successfully unmounted.

Performing fsck_exfat -y -x /dev/rdisk6s2

Checking volume.

Checking main boot region.

Checking system files.

Volume name is LaCie 4TB.

Checking upper case translation table.

Checking file system hierarchy.

Checking active bitmap.

Rechecking main boot region.

Rechecking alternate boot region.

The volume LaCie 4TB appears to be OK.

File system check exit code is 0.

Restoring the original state found as mounted.

Operation successful.

Running First Aid on “LaCie Mobile Drive Media” (disk6)

Checking prerequisites

Checking the partition list

Checking the partition map size

Checking for an EFI system partition

Checking the EFI system partition’s size

Checking the EFI system partition’s file system

Checking the EFI system partition’s folder content

Checking all HFS data partition loader spaces

Checking booter partitions

Checking Core Storage Physical Volume partitions

The partition map appears to be OK

Operation successful.

BenB wrote:

"Unix and Linux, AFAIK, don't."

You are aware than macOS is UNIX, right?

Yes, but at my last job we had hundreds of Unix boxes, and not even once, AFAIK, did anyone disconnect external devices (like NAS and SAN) to troubleshoot. Also, there are many "flavors" of Unix. I'd expect the least trouble from IBM's AIX, e.g. (We did have trouble with tape drives, but is there anyone who hasn't?! NTL, I don't recall ever having to disconnect one except to repair the drive itself.)

Also, FCP doesn't play well with ExFAT drives. Not sure why you'd be using one on a Mac anyway.

Yes, so I've read on some Apple FCP page. But it works fine anyway. I just tested it to be sure. It runs anyway.

I think the drive came formatted ExFAT; I don't recall for sure. Anyway, I don't really need FCLM to work on it. It's mostly a dump area for FCP libraries that I ought to delete, but am paranoid I might need one day. It would be nice if it did, but not essential. It is "essential" that FCLM work on the SSD drive.

ExFAT is useful for transferring files between Mac and Windows boxes. I recently copied a video file from my sister's Windows laptop. Worked great! (No, she doesn't know how to put it on OneDrive or similar, and I didn't want to fuss with it. So I just brought the drive to her place.) I also sent some video files to a friend on a thumb drive formatted as ExFAT. His internet skills are weak and he has a marginal connection to the internet on top of that (satellite that doesn't always work).

The drive I care about is a 4TB SSD formatted as an APFS drive. I bought it for the very purpose of holding FCP libraries! And now I am to ditch it, hoping to find one that FCLM works on?

I use FCLM couple times a week for years now, never any missed Libraries.

Yes, the vast majority of people have no trouble with FCLM. Arctic Whiteness told me they've seen 3 cases like mine. But I contacted them this time starting Sep 20. We had two separate discussions. Same thing: ~" They need to reproduce it. They need to make a special build that puts out more error messages. They'll ask the developer if he's willing to make such a build. They might need to control my desktop. It is not easy. ~" Well, I've given up on getting it fixed for free. So I am to ditch my expensive SSD and buy more and more of them until one actually works? Maybe I'll offer them $70. Maybe $100. Far cheaper than buying and trying various large SSD drives!

I think there's a deeper issue here.

Deeper issue? Everything else works fine on the drive except First Aid on the disk (outermost layer) says the EFI or something is bad and that it might cause problems booting from it. Well, when I boot my old Mac with it, it works just fine. It is only FCLM that has a problem with it. (Actually, when my internal HDD died [part of a Fusion drive] on my old Mac, I used this SSD to boot from. I did, however, have to disconnect the two backup drives I have for it to boot. Then I connect and mount them, and all was fine except I had to manually mount the swapfile.) (Come to think of it, I did have trouble with the SSD drive not showing up in the Finder's sidebar at the right time, but a quick fix in Finder Properties seems to have fixed it (see my post on that).

macOS is no more vulnerable to external devices than any other OS, and the troubleshooting of removing external devices is universal, not unique to macOS.

I've been using various types of computers using various OSes since 1985. I was system manager (system admin) for OpenVMS from 1994 thru 2010. I've assisted the Stratus admin (the OS there is called VOS). I helped with system admin work on Solaris Unix and Red Hat Linux boxes for almost a decade.

And not even once, not at all, in fact, exactly ZERO times with years of experience with various OSes: Windows, OpenVMS, Stratus (VOS), Solaris Unix, Red Hat Linux, have I ever needed to disconnect external devices as part of troubleshooting. ONLY on the Mac (well, I didn't have external drives on my Windows PC from 2000 to 2008; just a printer) have I seen troubleshooting instructions so often begin with "disconnect all your external devices."

Why post here? I found out about FCLM here, and hoped that maybe someone already had this problem and fixed it somehow, and could tell me the cure. But alas, nothing.

Anyway, thanks for chiming in.