000075 : Unable to store generated mask shape for <value> features.
For complex marker symbols, the Convex Hull method will fail to generate a shape when Margin is equal to or greater than a certain value. This value varies based on the reference scale and the units of measurement. In this event, there is no result created for the mask feature.
A smaller Margin value is needed to achieve a result. Temporarily increase the size of the marker symbol so that output mask features will simulate a large mask around a small feature.