Listbox / Viewport combo platter changed in 5.1.2?

Trying to figure out where to look for this issue. I’ve used identical code for our last three iOS releases (all built with some flavor of 5.1). I updated to 5.1.2 this morning, and my preset manager, which uses a Viewport / Listbox for fingering, will no longer display any but the first item of its array.

Debugging shows the correct number of files in the array, and I didn’t change anything. I’ve also updated to Xcode 9 so I could build for iOS 11; I can’t see how that would affect anything. I can’t find anything in the changes to imply either Array, Listbox, or Viewport was touched in the last update.

Any thoughts?

EDIT upon further reflection : it appears that paintListBoxItem is only being called once, rather than whatever getNumRows() is returning. Using getNumRows() as the iterator, on the left is the contents of the array, on the right, you can plainly see it only writing the first one:

Disregard. As expected, user error.