GL-AC1300 - Issues with Extender Network Mode

I’m trying to use the “Extender” network mode to extend the range of some equipment which has a WLAN interface (basically it just broadcasts an Access Point to connect to). There is no DHCP server present in the equipment either.

This works flawlessly with the GL-AR750S.

With the AC-1300, I get the following error after choosing the equipment’s access point:

The LAN subnet conflicts with the Wifi subnet to be connected, please set a different subnet.

I’m a bit confused by this as it was my understanding that DHCP is not involved in “Extender” mode - the radio interfaces are just bridged (as opposed to Repeater mode which uses the firewall/router).

After this error, the GL-AC1300 does not enter “Extender” mode but seems to be in “Repeater” mode:

Anyone have any ideas on this different behavior I am seeing? (compared to the old Slate)

EDIT: Firmware info:

Version 4.1.0
Firmware Type release7
Compile Time 2022-11-05 14:58:38(UTC+08:00)

I tested A1300 with release 7.

The first time it revert to repeater.

The 2nd time it goes to extender.

So it seems buggy. I will file a bug internally.
But can you try one more time.

Tried many times and can’t seem to get it to work unfortunately. Look forward to a fix!