In AM-2.6.1
yes, i have the same problem, keeping the key pressed right or left it does not scroll the images, just one by one
Yes, there was a change in the way Attract Mode manage "left" and "right" signals that are now non-repeatable, it was not clearly stated in the release notes and I missed that completely.
I'll see if there's a way to reimplement scrolling in Arcadeflow with the new way, although I fear it won't be so easy and probably different from what it is now. At the moment it seems that in my layout even "prev_game" "next_game" "prev_page" and "next_page" hotkeys are non repeatable for some reason

The only suggestion I can give is to stick with 2.6.0 while this get fixed if you really like Arcadeflow.