Can unbind but cannot bind back in zigbee2mqtt

How is binding supposed to work?

I have 2 4-gang light switches with only 2 lights for each, so and I was planning to bind buttons 3&4 on one switch to buttons 1&2 on the other switch and vice versa so I could control all lights from every switch.

Tried binding from the menu but no matter what I select the “bind” button is always greyed out.
Then I tried to unbind one of the default binds on one switch, and I cannot even bind that back.

What is going on there?