Hi community!

i have been using KMymoney for many years and I find it very good for individual finance management and also for one-person enterprises.
But today I noticed a strange thing in reports.
As in the past years I opened the report "Transactions by categories" and changed some report settings, in order to adapt it to my needs.
Filters
all filters as default, but date selects last year
General: as default
Rows/Coloumns:
- organise by categories (as default)
- show columns: Number, Payee, memo,
Other options: include only tax categories

The result shows the transactions involving categories with tax flag ("include on tax report") grouped by category -> that is regular.
But the the reports shows on the top all the "no-tax" transactions sorted by date, not grouped.
Why are no-tax transaction also listed?
How can I avoid this?

Thank a lot in advance for suggestions

Basic data
Operative system: OpenSuse Leap 15.4
KDE-Plasma: 5.24.4
KDE-Frameworks: 5.90.0
Qt-Version: 5.15.2
KMyMoney: 5.1.2