For around 6 months I had intermittent issues with my MacBook Pro (13-inch Mid 2012) where it was randomly ending up on the folder with a question mark icon, or the no-entry icon.

It used a 250GB Samsung 840 SSD - which I had installed in 2014 - and I figured it must have finally been at its end-of-life.

I've replaced it with a 1TB Crucial MX500 SSD; the swap went smoothly and as expected.

Now, I'm having problems installing macOS Catalina at all.

After installing the new drive I did the following steps:

  1. Downloaded the latest macOS Catalina from the App Store on my iMac
  2. Created a new Catalina Install drive using Terminal createinstallmedia
  3. Booted from the USB on the MacBook Pro
  4. Formatted the drive to APFS in DiskUtility
  5. Used the macOS install button, accepting terms etc..

The installer gets to around 50% normally (in around 5 minutes), but then it slows down dramatically, with the estimated time floating around 5-7 minutes constantly. The loading bar continues to move incredibly slowly (using the ol' cursor on the boundary of the loaded section to track progress).

This goes on for well over an hour, and at around 70% it fails with the error:

An error occurred while preparing the installation. Try running this application again.

I've taken the following troubleshooting steps so far:

  1. Reset SMC
  2. Reset NVRAM, PRAM
  3. Recreated the install USB pendrive
  4. Re-recreated the install usb on another USB pendrive
  5. Used different USB ports
  6. Online-recovery (defaults to Mountain Lion, which got all the way through the progress bar then loads to a folder with a question mark at mid-install auto-reboot)
  7. Cloning the old Samsung SSD to the new Crucial SSD in DiskUtility
  8. Numerous power-cycles, and letting the machine sit for a bit etc.
  9. Run health-checks on the old and new SSDs, both return no issues

The machine had otherwise been running great. Fast as always with no known issues with RAM, or battery life, etc.. I can't think of what else to try at this point.

The machine's also in near-new condition, it's been very well looked after. All the ports etc are clean and in good working order, as are the charge cables.

There are no Apple stores or authorised repair centres where I live (boat/flight required for the closest, which isn't an option due to Covid lockdown).

Any ideas on what to try next would be greatly appreciated, I'd very much like to see this MacBook working again.

Many Thanks


install fail point point where install slows drastically

  • 1
    It could be as simple as a bad SATA cable, but I don't actually know how to test for that, short of replacing it.
    – Tetsujin
    Jul 4, 2020 at 16:25
  • @Tetsujin I ran out of things to try, so I ordered a replacement SATA cable.. it appears to be working fine now, and macOS has installed. Strange that the OS otherwise installed fine, and read/write to the drive seemed to be fine for the most part, other than the slow-down during install. In any case, it looks like the SATA cable was indeed the culprit. Which is great news, as now I have a spare Samsung SSD which I thought was the original problem. If you add your comment as an answer I can accept it. Thanks for your input. A way to test the cable would be good...
    – Craig
    Jul 9, 2020 at 19:13

1 Answer 1


A rather brief answer…

A bad SATA cable could quite easily be responsible for all of the above aberrant behaviour - however I know of no way to test for that, short of replacing it & seeing if things improve.

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