Your'e welcome. I went to this road before and here is the trick: E-pub
is a set of bundled html pages and html don't like tab characters.
Therefore we must ensure to replace tab character by proper spaces. It
happens when you have lists, where the list number or bullet is followed
by a tab character. Fix is to change the list style, but it requires
inspection. Other than that, it looks quite well.
A sample of e-pub is available here
Note: Miklos Vajna from Collabora worked a lot on e-pub in 2018-2019
period. Worth a second look.