pcolor with shading interp, does not interpolate sometimes?

When I use pcolor for two different two regions which are nearby to each other. After this, If I apply shading interp to my figure, it cuts the values at the interface of both regions.

Thanks in advance.

[John D'Errico]

If you want help, it really makes it easier if you show an example of the problem. Help those who you would ask to help you.