MongoDb Grouped values are coming back null?

I'm testing out the Metabase with my MongoDb instance and am experiencing an issue with grouping.

For example, if I attempt to select all records grouping by CPU_BrandString which is a "type/Text"

It appears to be grouping the data correctly, and returning the proper counts, but the values of those entries are null.

The native query is:

But in the database, there are clearly values attached.

Any suggestions?
Thank you.

Once I flattened my structure I started getting results back.
Does Metabase not support nested objects?
Is there a Github issue for this?