Spatial Polygon File does not Intersect with Spatial Points File correctly in Tableau Desktop 2020.2

Issue

When very small/narrow polygons are used, spatial intersection does not work correctly.
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Environment

Tableau Desktop 2020.2 - 2020.4

Resolution

The small sliver polygons should be removed from the polygon file.

Open the polygon file in a geographic information system (GIS) or other tool for editing spatial files. QGIS is a free and open source option that works well for this.
If the file uses multipolygon geometries, convert them from multipart to single part
Calculate the area for the single part polygons
Delete the polygons with exceptionally small areas (typically much smaller than 1 square meter; generally in the order of 0.001 square meter)
Collect the geometry back into multipart polygons
Save your edits
Refresh your datasource in Tableau, or replace with your edited spatial file, and try the join again

Example below:
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Cause

The issue may occur when very narrow/small polygons are used.
This is a known issue in Tableau Desktop that is under investigation by development team.