@kiwidude,
I'm a regular user of ePubFixer. Just in case it helps I've attached a before-and-after version of the cover xhtml file. The 'before' is from a retail epub which has not been calibre converted.
The 'after' example is following use of the ePubFixer 'Edit Cover' option with 'Preserve Aspect Ratio' unchecked. If it had been checked the only difference would have been
Code:
preserveAspectRatio="xMidYMid meet"
rather than
Code:
preserveAspectRatio="none"
Before
After
(I've deliberately obliterated the 'urn:uuid:' code in case it revealed personal stuff???)