I think there is still an issue with the HeatmapRenderer in 3.12. Perhaps it is related to an issue discussed in 3.11 by Ken Buja and Bjorn Svensson.
It happens when the map extent is smaller than the available space in the div, as shown with the empty white space on the left and right side. In the sandbox I commented out line 59 so that I could zoom out far enough to show it.
Working fine so far...

...but then zoom out so that the map is smaller than the div. Data on the east side of the international dateline is dropped:
