excessive time to copy file to external hdd

This is a strange situation. I am trying to use file manager to copy a 60gbyte file from macintosh hd data to an external had and the estimated time is around 4hours and the copy status seems to support the estimate. I tried to copy the file from one folder to another and it also shows a 4hour estimate.

I did a copy / paste of the file to a different folder and that was quick but then then attempted to copy the file to the external hdd and its estimates and performance is similar to the first two.

I have a program I use to sync folders (goodsync) and when I use this program to copy the file it completes very quickly. I’ve run disk utility on both drives and they seem to be good. I’ve run apple hardware diagnostics and they show no issues.

any idea why a simple copy of a 60gbyte file is estimated to take 4 hours?

the iMac is a late 2015 27” iMac running Big Sur. The iMac hard drive is a 3tb fusion drive.

I did a clean install of Big Sur about 2 weeks ago to address a broad performance issue that I have not resolved totally.

any suggestions?