Just bought DIR-510L flashed to 1.06. Tried to use it whilst staying at a Guest House. Would not let me connect because their access point had a long password.
Did some testing when I got home and setup a Hotspot and confirmed it does not like long Passwords works fine with 8 characters so "Qwerty12" works but "Qwerty1234" does not.
This is "Travel Router" so needs to be able to connect to hosted Wifi. Needs fixing could you escalate it with your developers please.