All of a sudden I've been getting a -43 error code on my MBP & iMac when attempting to delete/remove files.

What might I have done to cause this and is there a fix?

-43 means "file not found." If you try to delete a file and see this, it means the system can't locate the file you're trying to delete, which often means serious directory corruption.

I'd start by using Disk Utility to verify and repair that drive. Report back with what it says.

I booted to a backup volume and ran DiskWarrior 5.0. My main volume’s Optimization Index was “10”, so I was not hopeful that continuing with the repair would be beneficial. But I did it anyway.

The result was that “60 Files had a directory entry with an incorrect text encoding value that was repaired.” All 60 files looked like this (but with differences in the file numbers):

File: "ヒラギノ明朝 ProN W3.ttc_ATS_692_266870060
"
Repaired Text Encoding
Location: "Zeus/private/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T/TemporaryItems/"

After allowing the repair, the -43 error issue was resolved.

FWIW 1: I have used DW for many years, but always it was as a preventative measure. AFAIK, this is the first time it resolved a problem after the fact.
FWIW 2: Disk Utility was of no value.

Once again, kind sir, many thanks. Always, your time and expertise are greatly appreciated!

The Optimization Index simply tells how fragmented the directory is. It does not address directory corruption. Fortunately, DW was able to repair it.

As I understand it, directory fragmentation is not nearly as important as corruption so don't assume that a score of 10 means that you don't have a problem.

Gads, more I did not know. Can there be other things in life that have eluded me? Nah...

Truly, that is good info, Jon. Indeed, I will keep it in mind!

The -43 error returned (in the night) and I was able to resolve it by (merely) restarting.

FWIW, I subsequently ran DW, but this time no errors were found.

Can it be that something other than HD corruption is at play?

Error messages are not always correct interpretations of what is happening and often they are madningly uninformative. Additionally there are several things both permanent and transient that can raise and error -43. Have you looked in the log files to see if there is more information there?

DW is an excellent utility, arguably the best at volume repair, but a volume scan or repair is not all inclusive in detecting possible errors and does not give a complete picture of the drive's long term health. A full report of all the S.M.A.R.T. Values, not just the summary pass/fail can tell you a lot more about the drive's long term health picture and a surface scan reveals even more. The only tool I am aware of that does both — in addition to volume scan and repair — is TechTool Pro 9.

If I were in your shoes I would look carefully at the system log files for some indication of what might have given rise to the error -43 conditions and because I already have TTP 9 I would run a complete suite of tests including the full set of S.M.A.R.T values and a surface scan — just to be sure of the drive's continued long term health.

Thanks, Joe, for the TTP 9 tip; I would not have thought of that. And indeed I'll give it a go, but want to wait until it is Sierra compatible.

I have reviewed my system log, but either found nothing significant or didn't comprehend what I was reviewing.

TechTool Pro 9 IS Sierra compatible and adds new testing and repair features.

Joe,

The source of my doubts/confusion re compatibility is this note at the bottom of the Maintain/TTP site: "OS X 10.8 or greater, macOS 10.12 'Sierra' support coming soon."

And, when I launch TTP 9.0.1, I get this alert: "TTP Pro (version 9.0.1) has not been tested with Mac OS x 10.12. Please confirm that you are running the latest version of the program."

Where did I go wrong?

Here's a link to Micromat's note about v9.0.1 and the warning: Sierra compatibility

There is this statement about TTP 9 on the Micromat web site When I launcned TTP 9 (I am on my iPad so I don't know the exact TTP version) on MacOS 10.12.1 beta 2 I did not get the warning message. I suspect app developement has gotten ahead of web site updates.

I'll be taking your advice Joe, and running TTP today. But what specific tests do you think I need run? Of course, if I need to run them all, I will.

I moved a branch of off-topic posts to a separate thread: AppleFS, fragmentation, and SSDs

If you have plenty of time — like starting just before bed and ending before the alarm goes off in the morning, the full system will test everything from the standard volume checks, partition maps, S.M.A.R.T., surface scan, memory, video, processor, bluetooth, network, fans, sensors, and I am confident I am missing some.

If you just want to assure yourself of the long term health prospects of your HD or SSD then I would start with S.M.A.R.T., and look at all of the reported values. If any of them are in the red range or if there are multiple in the yellow range I would start looking for a replacement drive. (Personal opinion I would get an SSD even though an HD would be cheaper.)

Regardless of what S.M.A.R.T. reveals, if the Surface Scan (remember that can take a while so don't get impatient) detects new bad data sectors, I would also be in the market for a new SSD. New bad data sectors is an indication the magnetic media is flaking off the platter and will only get worse over time.

Failures or warnings on the other tests will reveal more esoteric, and unfortunately likely more expensive problems with various other hardware systems.

NOTE: Generally testing can be performed on the boot drive, but repairs have to be run from another boot volume and often testing is more accurate when performed from another boot volume. Either the E-Drive or IMHO even better a ProToGo boot volume on a USB 3 Flash Drive will fill that need nicely and ProToGo is now an "in the box" part of TechTool Pro 8 or 9.

Sorry, Joe, for being so tardy in getting back to you.

I ran the full suite of TTP tests, but I wanted to watch what parameters and such are being tested, so I did the tests individually.

On the plus side, I'm most pleased that everything passed with flying colors.

And for reasons that elude me, the -43 error has ceased and all works as divined. That such can be transitory is a mystery. I guess I'll need be more attentive and watchful for unusual events in hopes that clues surface. Unless, of course, you suggest otherwise,