Errors existed even in 1970, after the show was long gone. The problem was that GK outsourced a lot of their artwork to European artists who never saw the show (this was also evident it the VOYAGE TO THE BOTTOM OF THE SEA series). They worked from photos, and one of the reference items must have been James Bama's mid 1966 promo done before the show premiered (lower right).
Bama also only had stills to work from, and it it seems he thought that , like any good spaceship, flames should shoot out the back of the Enterprise. Even from the shuttle deck.
Alberto Giolitt's Enterprise also belched flame in issue #7, from 1970. The Enterprise also had a very tight orbit around earth, damn near grazing the Eiffel Tower. I won't even harp on the Captain's Log stardate format being all out of whack.
Here are some more panels, from issue #9, also by Giolitti (The story this issue , btw, is by Len Wein)