Description:
When batch-attaching host groups in multi-threaded mode (with 4 CPU threads), the operation fails with an error (see screenshot). However:

• The same operation succeeds in single-threaded mode.

• Batch-removing host groups in multi-threaded mode does not exhibit this issue.

Steps to Reproduce:

1. Enable multi-threading (4 threads).

1. Attempt to batch-attach multiple host groups → fails.

1. Repeat in single-threaded mode → succeeds.

1. Batch-remove host groups in multi-threaded mode → succeeds.

Expected Behavior:
Batch operations (attach/remove) should work consistently in both single- and multi-threaded modes.

Environment:

• Zabbix version: [7.0.10]

• CPU: 4 threads