MacOS – Move contents of one directory to another

It's not an answer to your specific intermittent failure, but I do have a workaround that several clients have used.

I make them another account that isn't file vault protected and rather than logging out and leaving the mac at the welcome screen, enter the empty user and walk away. (or kick off a backup and then walk away)

In practice I get better backups when a user is logged in.

If this needs to work for you, do file a bug with apple since it should work each time and every time without a workaround. When it fails, there should be detailed enough logging to fix issues if they arise even if normal logs are suppressed as a compromise to added security with FileVault enabled.

Also BackupLoupe is great for poking at backups to see what is actually changing after the fact rather than guessing from logs and byte counts stored in logs.

I have had other people reconsider file vault and just use encrypted disk images for data that needs to be secured which minimizes many of the drawbacks of having the entire user folder inside file vault. I've done this myself since soon after file vault came out and I much prefer it compared to living with FileVault.

hm. Removing my answer, because not helped.

So - you got a message into Console.log. So, come step-by-step. :)

What return this command?

lipo -detailed_info /System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Contents/MacOS/quicklookd

Should this:

Fat header in: /System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Contents/MacOS/quicklookd
fat_magic 0xcafebabe
nfat_arch 2
architecture x86_64
    cputype CPU_TYPE_X86_64
    cpusubtype CPU_SUBTYPE_X86_64_ALL
    offset 4096
    size 504912
    align 2^12 (4096)
architecture i386
    cputype CPU_TYPE_I386
    cpusubtype CPU_SUBTYPE_I386_ALL
    offset 512000
    size 399280
    align 2^12 (4096)