Details: When I have a split pane and both "sides" (the normal app and the pane) have a single container, expanded to fit, and the container in the split pane has a particularly lengthy body, the app's "main" section appears to regain it's scroll bar, despite the "Expand to Fit" option being enabled for both containers. Scrolling down on it scrolls "past" the app (hard to explain).
The key here seems to be that the body of the container in the split pane would definitely scroll beyond the expanded container. It doesn't happen on containers with more reasonable vertical lengths, but unfortunately some of mine are unreasonably long.
The one difference I immediately notice is that the footer is missing on the right container (the one with all the containers inside it). Both left and right is set to "Expand to fit"; can't tell if that's the case here. I can't tell how many containers you have on the right, but I assume you tried adding them continually to see if there was an issue. I'll keep looking and see if there's anything else I can come up with. Scroll should be hidden in all cases.
