Created attachment 193340 [details]
2 Pivot Tables: one with group Spiel2, and one where to group some dates

+++ This bug was initially created as a clone of Bug #160393 +++

PRECONDITION (same as Bug #160393):
see attached Pivot-Spielergebnisse-Dual.ods (same as Bug #160393)
The Items "Halma" and "Kniffel" in a Row Field were "manually" grouped, 
i.e. these 2 Items marked and grouped with Data > Group and Outline > Group... (or F12),
the 3rd Item "Schach" is grouped with a single entry, 
the original Row Field "Spiel" is removed from the Row Fields. 

PROBLEM DESCRITION:
creating a grouping in the second table (which has the same source data) 
removes the grouping of the first table

DETAILS:
in the attached Pivot-Spielergebnisse-Dual.ods
there are 2 Pivot-Tables (source data for both is $Spielpunkte.$A$1:$E$55):
- left Table at G4, where the Row Field "Spiel2" is a grouping of the category "Spiel"
- right table at P4, the same Pivot-Table without grouping 
when adding a grouping in the right Pivot-Table:
- mark several dates in the Row Field "Datum" and Data > Group and Outline > Group... (or F12)
the grouping "Spiel2" in the first table is lost.


Version: 24.2.1.2 (X86_64) / LibreOffice Community
Build ID: db4def46b0453cc22e2d0305797cf981b68ef5ac
CPU threads: 2; OS: Linux 5.4; UI render: default; VCL: gtk3
Locale: en-US (de_DE.UTF-8); UI: en-US
Calc: threaded