disk utility restore fails - Could not validate sizes - File too large

Do this:

Drive Partition and Format - El Capitan or Later

1. Open Disk Utility in the Utilities' folder.
2. After Disk Utility loads select the drive (out-dented entry with the mfgr.'s ID and size) from the side list. 
3. Click on the Erase tab in the Disk Utility toolbar. A panel should drop down.
4. In the drop down panel set the partition scheme to GUID. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
5. Click on the Apply button, and click on the Done button when it is activated.

Clone El Capitan and Later using Disk Utility

1. Restart the computer and at or before the chime press and hold down the Command and R keys until the Utility Menu appears.
2. Select Disk Utility from the Utility Menu then press the Continue button.
3. Select the destination volume from the left side list.
4. Select Restore from the Edit menu of Disk Utility. A panel will drop down.
5. Select the source volume from the drop down menu in the panel.
6. Double-check you got it right, then click on the Restore button.

Destination means an external drive. Source means the internal startup drive.

I have the exact same problem, trying to clone a 1TB Fusion Drive from my Late 2015 27" iMac to a 2TB OWC SSD and I keep getting this error.

"Could not validate sizes - File too large"

"The operation couldn’t be completed. (OSStatus error 27.)"

Nothing useful on the internet. This sucks. Trying CCC next.

On a 2010 MacBook Pro, formatting an External Seagate HDD that is of 4TB Capacity --- was of success. I used secure erase (Max times over) and encryption, it took 30 days to securely erase it. Ridiculous, but so.

Point Being --- It worked twice for me using a 4TB Seagate External HDD.

How is the external disk formatted?

Why not use the free version of SuperDuper! to clone the drive?