I believe there's a bug in the Progress Summary due to a recent update.
When I use the filter "group by year" (or month etc.), only sorting by the first column really works.
If I click any other column header (e.g. activities count, total distance), it merely switches the sort direction, but the rows remain sorted by year.
Example screenshot - results should be sorted by the number of activities in descending order, but clearly that's not the case:
Tested in current Chrome and Firefox, no difference.