Reporter - Main Group Dropdown - Duplicates results

Hello Guys

Quick one I hope,

When writing a report I can see the main group dropdown that I can select what I want the grouping to be

Within this example I am using a date field that I have changed the format to y-m

When running the report it seems to duplicate the report results into the grouping

Same story on v 7.7.6, I suppose this is a bug!
In my test I use Leads and Main group the Report on Status, then I get also this unneeded duplicating!
Testing a bit more here and I think I see a second problem:
When I uses Created By or Assigned To in the Main group of the Report, then I see Record ID’s in the report instead of Created By/Assinged to. And again also the duplication.

Somebody else can confirm this and need to make a case in github?

Using report in 7.7.9

Grouping works for all field types but Date