Some permissions fail with aggregation

I have a situation with permissions and aggregation working with Views.

In my Views preview and from my admin account, the following set up works from my admin account:

Field 1: Category Name (aggregate: value)
Field 2: Category # (aggregate: entity id)  
Field 3: Products assigned to category (multiple values, rewrite "not assigned" when empty) (aggregate: target id)

Filter: Contact Message Type: Category
Aggregation: Yes
Permissions: Roles / admin, registered user

This is a Google scatter chart:
-Field 3 is the label
-Field 2 provides the data, and
-Field 1 is a grouping header

However, when I view the same chart as a registered (but non-admin) user, I get the following error:
All series on a given axis must be of the same data type

Poking around, I've discovered that the aggregation setting on Field 1 makes a difference - if it's pointed to the Entity ID, the chart displays fine in the registered user site. Pointed to Value and it breaks.

The problem is that when Field 1 is aggregated on the Entity ID, the chart only displays items that have products assigned to them and it ignores the rewrite on empty fields. I need the chart to show the full list, which it does with admin permissions.

I have tried converting the chart to both an unformatted list and a table, and both display correctly in the registered user site, so I'm thinking this is a role permissions problem.

Can anyone help?