Can someone from Draytek technical support comment on this, please??

It is said that Draytek staff don't read these forums, the official stance is raise a ticket with support.

I got my problem sorted by doing these steps

1. Hard reset the router (holding pin for five seconds)
2. Using the wizard to setup both 2G and 5G WiFi network. Disabled guest WiFi in my case.
3. Using wizard, I setup my ADSL broadband setting.

No more incorrect password when connect to WiFi. I noticed if you manually configure WiFi (without using wizard) using separate 2G and 5G section of WiFi setup page, it gave this weird “incorrect WiFi password” issue. Hope it help.

Don't bother thinking the new FW update for the AP910C to 1.2.4 makes any difference.

With the availability of new firmware I had high hopes it might have been the AP's causing the Wi-Fi password issues, re-activated the Wi-Fi on the router (which is at fw3.8.8.2) and still the exact same thing happening.

Come on Draytek this must be easy to replicate.

fw3.8.9.2 is coming with improvements (only available on US website so far)...

One of the release note points...

"Corrected: The wireless device was able to connect to WLAN (2.4G). After disconnecting WLAN (2.4G), the device was unable to reconnect to WLAN (5G) and received error message of wrong security key."

Is this the answer to our prayers?