Ray,
I finally got around to running the checkout wizard on a slower computer, but the result did not change.
iMac (21.5-inch, Late 2012)
8gb RAM
2.7 GHz Intel Core i5
Can we try some of the things you suggested?
Mac OSX 10.13
Dreamweaver 2018 (new install)
eCart 6.12 (new install)