Steps to reproduce:

1. Install a Zabbix Server v5.0 (LTS);
2. Set up some services ("Configuration" -> "Services"), for example:
   1. "LDAP pseudo-cluster": has the status calculation algorithm as "Problem, if all children have problems";
   2. two child services: "ldap1 node" and "ldap2 node" with the status calculation algorithm as "Problem, if one child has a problem";
3. Perform on-site upgrade onto Zabbix v6.0;
4. After Zabbix server v6.0 is started and the database has been converted, look at the menu "Services" -> "Services" and check the appropriate services.

Result:
The calculation algorithm "Problem, if all children have problems" has been converted onto "Most critical of the [any] child services", but "Problem, if one child has a problem" – onto "Most critical if all children have problems".

It causes to the wrong parent service calculations when the child is failed.

See the screenshots attached:

• "all children" in v5.0:
  
• the same service after conversion in v6.0:
  
• "one child" in v5.0:
  
• the same service in v6.0:
  

Expected:
Just opposite conversion: