EX3800 Extender mode (WPS) won't go off

EX3800 won't switch from extender mode to access point mode ONLY. "WPS" light is always on, no matter what I do. "Router" -light also turns on, so access point mode is starting, but same time "WPS"-light is still green. I have tried to push WPS-button for 5 sec so that green light starts to blink. Power-light goes orange, and turns to green after a while. But after blinking, WPS-light is always on, while router-light gets off and on, switching normally as it should. According to manual, WPS-light and router-light shouldn't be green at same time.

EX3800 is connected to Netgear WiFi-router with ethernet-cable, from main building to another. I need to expand my Wi-Fi with cable, because with extender mode the EX3800 can't reach the router on air. I made setup first time, by connectin EX3800 to router in same room with short cable. Setup worked out fine. Router light was on, WPS off and everything worked nicely. Then I moved EX3800 to another building and made same cable-connection. Only difference is that cable lenght is longer, as I use ethernet sockets in walls. EX3800 found the router as earlier, but now the WPS light won't go off. I also pushed factory reset and made setup again. Same result, WPS light is green and won't go off.

(NGEX3800ACRP, firmware updated)