The heatmap symbology is dynamically re-rendered when zooming, even if the Method is set to Constant and the Lock radius at specified scale has been set to a reference scale to prevent the heat map from changing across scales.

Workaround

Refer to this documentation https://pro.arcgis.com/en/pro-app/latest/help/mapping/layer-properties/heat-map.htm#:~:text=the%20color%20scheme.-,Convert%20static%20heat%20maps%20to%20raster,-Heat%20map%20symbology for information.

Steps to Reproduce