EasySolar-II GX shots down AC1 while transferring from grid to battery

Hello there

I have an EasySolar-II GX 48/5000/70-50 inverter with a Dyness DL5.0C - 51.2V battery. The CAN bus is enabled, so the inverter sees the battery and its BMS.

When the grid goes off, the inverter switches to battery power, but there’s a noticeable pause (about 3-4 seconds). When grid is restored, the transfer from battery to mains power is seamless.

The UPS function is enabled in the settings.

What can I do to avoid a short outage when switching from mains to battery power?