Now I am on repeater mode since I found it to be more easy to debug.
The moment I add a virtual interface I lose the WAN IP, similarly if I select 40 MHz. Revert them, then the Repeater is back in a minute - very consistent, How to explain that?
One thing unique to my situation is I am repeating a repeater. and this primary repeater is on non-ddwrt (stock) firmware.
OK, more info:
In repeater mode:
When I add virtual interface it works on 20mHz mode.
when I select 40mHz with virtual interface, then also I get wan IP on router, but computer(s) connected over LAN/WLAN (pry/virtual interface) can't access internet or local routers.
I think this is unusual to fail with changing to 40mHz all other things remaining equal, any clues?