I have a late 2015 27” iMac with a 2tb Fusion drive on Catalina. Fusion drive went out and the actual on-board SSD part of the board is the one that’s showing the errors not the 2TB HDD drive. Took it to a technician to replace the Fusion drive with a 2TB SSD, cost me $500+ tax, has been there now for two weeks and he cannot load Catalina on it again or my Time Machine back-ups. He never removed the SSD part of the Fusion drive, which the disk utility said was bad and I’m thinking it’s still trying to boot from it. It just keeps looping. I’m telling him he needs to open it up again and physically remove the Fusion SSD also and that might let the new 2 TB SSD be the boot drive. Is that necessary if that’s what bad?