Nothing 'complicated'
there, just more.
You asked an 'Automated program' to do (a best) job converting.
Only YOU know where you will accept compromize.
BTW you said 'Made an EPUB'. If you Created an EPUB (from scratch), You made also made all those styles
I think you Converted something TO an EPUB. What you get is expected to happen during a conversion.
There is no substitute for a Humans (in some cases: at code level) intervention
Repeated use of an image (eg fleuron) usually treats the as separate images. Tip: place the IMAGE only in one location and place a 'marker' (dummy paragraph) in all the rest of the locations. after conversion to EPUB, use the EDITOR to replace the markers code with the code from the 'Placed image'. . I t is a lot easier to do this way, than find and back out all the 'extras'