Looker Zip Code Heatmaps not Correctly Rendering in Drill Modal

[zephschafer]

We currently provide a map visualization in a dashboard that aggregates data to US States, using the Static Map (Regions) chart. When users click on individual states they used to see a heatmap of the data at the Zip Code level in a Looker "Drill-down" modal. However, following the breaking change in Looker's April 10, 2024 release this drill-from-state-to-zip feature stopped working for our users. When we manually toggle the "Enable Legacy Maps" feature to "On" in our Looker instance settings, this heatmap continues working; when we turn it off, the drill stops working. The trouble is that we are not explicitly invoking a legacy map anywhere in our code or settings. The behavior is as though  the zip-code drill-down option in the Static Map (Regions) chart provided by looker still points to legacy maps or, perhaps, the bug is in the `map_layer_name: us_zipcode_tabulation_areas`. Either way it seems that Looker is still connecting us to a legacy map feature in a way that we cannot prevent. Has anyone encountered anything similar? Or is anyone able to help us figure out how to address this issue?