I upgraded to version 2.60 on my iPad Mini 2 running iOS 11.2.1. Somehow I lost the ability to split the screen. I've tried killing and relaunching Accordance multiple times, had it clear the current session and download caches, turned off and rebooted the iPad, and even upgraded iOS from 11.1.2 (where it was when I updated Accordance) to 11.2.1, all with no effect. Of course, rotating the iPad doesn't solve it either.
The navigation arrows on the bottom toolbar appear to be offset slightly to the right from the center, as if Accordance thinks the screen is slightly wider than it actually is, pushing the split button off the right side.
Just after I wrote this, I had an idea. I turned off the new Page Turning feature, and the toolbar corrected itself after I selected a different text.