Mostly like it is a bug.

Pls do this:

When you cannot connect to the router, press and hold the reset button for 3 sections until the LED flashes faster to reset it back to Router mode. So that you can configure it again.

In router mode, go to repeater section and remove all saved SSIDs. And turn off auto scan and connect.

Then set up Extender again.

If this happens again, pls reset it to router mode and ssh to it and get logs:

cat /etc/config/wireless
cat /etc/config/network
logread