Saving graph as PNG blocked

[neilh10]

While doing a working view of data collected on a real stream study,
https://monitormywatershed.org/tsv/TUCA_PO03/4802/
I attempted to save the graph using the three horiz "Chart Context Menu" on the top right, as a PNG
It generated a "blocked screen"

The workaround, is to regenerate the graphs and then use the snapshot editor to capture it