ID 294373 - Iridescence Materials do not work with Group Masks

Problem summary
Iridescence Materials don't work with Group Masks.

When having an Iridescence material applied, if you try and mask it out using a Group Mask the Iridescence effect completely disappears.

Customer reported version
modo.13.1v1

Customer reported platform
windows10

Steps to reproduce

1) Open Modo and create a simple sphere.

2) Go to the Shader Tree and create a group.

3) Add an Iridescence material to this group. Notice how it affects the whole geometry.

4) Add an image and set the effect type to Group Mask

5) Notice that the Iridescence effect is no longer shown.

Expected behaviour
Users should be able to mask out the Iridescence effect.

Actual behaviour
The group mask makes the Iridescence effect completely disappear.

Workaround
Unknown.

Reproduced by support

This bug has been reproduced in:
13.1v1 - Windows 10 - MacOS 10.13 - Centos 7

13.0v1 - Windows 10

12.2v2 - Windows 10

12.1v2 - Windows 10

12.0v1 - Windows 10

11.2v3 - Windows 10

11.1v1 - Windows 10

11.0v3 - Windows 10

10.2v4 - Windows 10 - MacOS 10.13- Centos 7

Earliest version tested

10.2v4 - This issue appears to be in all versions of the product.