Yes, I confirm I'm seeing this. Not just duplication of page numbers, but sometimes also the opposite – jumps by 2 or 3 (instead of 1) when you flip the page, or even (on the 13-inch iPad Pro) jumps by 4 pages with a single page flip. I must say this only seems to occur in malformatted EPUB files, and it only occurs with the "pages in book" data – whereas "pages in chapter" seems to be 100% reliable. I reported this bug to Kris a week ago or so.
And no, I don't believe Jon's beloved "ADE-style page numbers" is the solution.
Adobe? 
Now I'm shuddering... Please let's stay away from "anything Adobe". On the other hand, if Kris implements "ADE-style page numbers" later on to humour Jon and perhaps other Adobe fans, I have nothing against that, as long as the ADE-style would remain purely
optional in Marvin. I would
not switch to ADE-style page numbering even if it
were available in Marvin right now. Like Kris himself, I very much prefer the "real-life" calculation of "pages left" that Marvin 3 attempts to do currently, even though it is buggy. But it's very nice to see that the same book may have 450 "pages"/screens on the 8-inch iPad mini, but only 280 "pages"/screens on the 13-inch iPad Pro, because that (unlike ADE-style page numbers) actually corresponds to the real-life sizes of those reading devices.
