So the numbers for the end-notes are actually being generated by an ordered list (<ol>) element? That seems to over-complicate things unnecessarily, but yes... that code falls right into the classic "
not gonna work well in a MOBI" trap. The <li> tag is responsible for creating the numbers for your end-notes and the anchor tag
follows that <li> tag. That just won't work when you jump right to that anchor-point via a link. The anchor must precede
everything that you're attempting to link to. In this case, that includes the <li> tag (and it still might not work even then since the <li> tag is a child of the <ol> tag; I'm not exactly sure).
I'll be honest... I don't know what the best approach would be to solve your particular issue without just ripping out the ordered list entirely (which I highly recommend if that's
at all an option).
EDIT: And no... back links aren't
really 100% necessary for most eink Kindle devices themselves (back button), but I can't vouch for the Kindle apps (Android/iOS... etc.)