Description:
If you do a mail merge into labels with multiple "Next Record" fields from different database, the results are totally wrong.

Note: This is about LibreOffice 7.5.2.1 but that's not a choice in the version list.

Steps to Reproduce:
1. Create a spreadsheet with two cells: A1="field1", B1="value1". Save it as "calc1.ods".
2. Create and register a database called "db1" connected to it.
3. Create a spreadsheet with two cells: A1="field2", B2="value2". Save it as "calc2.ods".
4. Create and register a database called "db2" connected to it.
5. Create a labels document with this in it, synchronized across all labels:
   DB1: <field1><nr1>
   DB2: <field2><nr2>
   Where "field1" and "nr1" are fields from db1 (the latter is the "Next Record" for the database, and "field2" and "nr2" are from db2.
6. Print to mail merge into a file.

Actual Results:
The first label in step 6's output file looks like this:

DB1: 
DB2: value2

The first label in step 8's output file looks like this:



Expected Results:
The first label in the output file should look like this:

DB1: value1
DB2: value2


Reproducible: Always


User Profile Reset: Yes

Additional Info:
Version: 7.5.2.1 (X86_64) / LibreOffice Community
Build ID: 50(Build:1)
CPU threads: 16; OS: Linux 6.1; UI render: default; VCL: gtk3
Locale: en-US (en_US.UTF-8); UI: en-US
Ubuntu package version: 4:7.5.2~rc1-0ubuntu1
Calc: threaded