Catalina - Unable to Install Bootcamp
The HDD in my wife's Late 2013 27" iMac began to fail. Original build is Fusion Drive - 128GB SSD + 1TB HDD. I replaced the failing Seagate 1TB HDD with a 1TB Samsung EVO 860.
Based on recommendations elsewhere before I installed the new 1TB SSD I effectively split the Fusion drive by separating the 128GB SSD from the HDD. Now there are two drives listed: 128GB Apple SSD and 1TB Samsung SSD.
I performed a clean install of macOS Mojave (as that was the most recent OS loaded) on the Samsung 1TB SSD. After installing fresh copies of all of the applications, transferring all of the files, etc. I updated it to Catalina and it runs quite well.
As there are a few Windows applications she would like to run I thought I'd install Windows 10 via Bootcamp on the unused 128GB SSD.
Unfortunately I've run into a number of Bootcamp Assistant errors, all involving the creation of a USB installation disk. I've properly formatted and tried several 64GB or larger USB 3.0 thumb drives in different USB ports. Either BCA indicates it can't read the drive, the drive is too small or midway the attempt fails with an error saying that the activity couldn't be completed.
All of the issues arise prior to even attempting to use the "spare" 128GB drive as a Windows boot disk.
I've tried the same steps on my Late 2017 27" iMac (also Fusion drive) running Mojave and it works fine. I'm wondering if this is a Catalina issue or...?
I've searched here and elsewhere but not found any threads that match the issues I'm experiencing. Any advice would be appreciated.
TIA!
iMac (27-inch Late 2013)
3.5GHz Quad-Core Intel Core i7
32GB 1600MHz DDR3
NVIDIA GeForce GTX 780M 4GB
macOS Catalina v10.15
iMac Line (2012 and Later)