Minimap corner thumbnail map on gigapixel image gets cutoff

Reported in Zendesk #4372. The zoomify image in question has the following image properties:

<IMAGE_PROPERTIES WIDTH="6375" HEIGHT="3924" NUMTILES="543" NUMIMAGES="1" VERSION="1.8" TILESIZE="256"/>

With Treat-as image setting in StoryMap, the edges of the minimap view are being cutoff. Some of the navigation points are actually near the edges of the map and are thus not showing in the minimap, making the cutoff problem worse from a UX perspective.

It is not clear if there may be problems with the zoomify image or tiles itself, or if this is just a problem in the leaflet code that has not surfaced before now.

Tiles for this zoomify image are not consistently 256 pixels as indicated by image properties, although there is some indication that edge tiles should not be expected to necessarily match the tile size.

Current theories are that the issue lies specifically in the leaflet code which we may or may not have control over. Further investigation needs to be done wrt the zoomify image specifically. It is recommended that a new StoryMap be created from a distinct zoomify image which replicates the properties of this image as listed above. Given this new StoryMap with a different image of the same properties, do we see the same behavior? If we lay points near the edges, do these fall off of the minimap view?