same Problem here! I got a message, that a newer firmware version is available and I downloaded and installed DIR655A4_FW136EUB01.bin on my DIR-655 Hardware A4.
After installation with success message, I wasn't able to change any Network settings of the router because of the same message, wprins described earlier: "AP should not be locked before configuring". There seems to be no setting to avoid this message. Searching this message text via smartphone brought me to this forum.
I did not make a factory reset before, but the router reported a successful update and he also let me in. After the update and the mess with the described problem, I did a factory reset, but this brought nothing.
So I changed the firmware back to 1.34EU like it was before. Now all is OK again.
Until now, with 1.34EU I had the problem, that the Router sometimes refused to reconnect to a DNS Server, after he had lost the connection one time. I originally hoped, that the newer firmware could fix this. But this was a flop. The pity is, that If I don`t want to get a EMail daily about the new not-working 1.36, I will have to turn off the Notification.