Revisiting blogs...
Using Jamroom
OK I know why this is happening, and unfortunately there is no "easy" fix for it - the issue is that we are trying to group by a column that is in a table that is being joined to the main item table (in this case the _profile_id) - which is at the core of how the DS works.
So there's really no way currently to make this work AND have the results be paginated. Instead, what we will have to do is setup something like JR4 had - i.e. something like max_per_profile="1" (or something like that). The problem is that when doing this you can't paginate, since it has to pull down MORE results than will match, and then "prune" in the template display loop, which breaks pagination.
So I will look into something like that for the jrCore_list support.
Hope this helps!