Hi,
To clarify your situation, could you let me know the brand and model of the UPS units and whether dedicated management software is installed on both computers? Also, do the monitor flickers occur only when the UPS is running on battery, or do they happen even when it is fully charged and plugged in? Finally, have you checked whether the "Microsoft ACPI-Compliant Control Method Battery" appears in Device Manager on both computers or only on one?
Kind regards,