I found out that this bug was not fixed in 5.5. I tried now to make the same hack as in 5.31. The bug could be fixed with this as shown at the tp of this therad ( by adding <input type="hidden" name="date" value="$date" /> in the template).
However I could not resolve the second problem described above with "group by member". I applied the code change (which worked for PP 5.31), but in PP 5.5 it does not work.
How can I fix this in 5.5.?
Thanks in advance