I have a RE590T and have run into the same issue. This completely breaks my desired use case, with absolutely no technical justification as far as I can tell. If it can't be worked around, I will be returning my purchase.

To be clear, I want to use my device to connect to some upstream host network, such as a hotel wifi. I then want the device to broadcast its own network with a DIFFERENT WPA-PSK password, because I want this password to be constant even if I change the host network settings. The entire point of getting a range extender for my use case is to have a single device that I update the network settings for, and then all my other devices connect to it with the same static authentication keys that never change based on location. Having to update the password each time entirely defeats the purpose.

So let's say my hotel wifi is 2.4Ghz with the SSID "Hotel" and password "123". I want to be able to pull the device out of my suitcase, plug it in, enter "Hotel" and "123" as the host network, then automatically have the range extender act as a router for my own personal network settings on both 2.4Ghz and 5Ghz channels. My phone, my laptop, my portable server, my portable video player, etc. all just automatically work with the same settings I use at home, since the extender is using my home SSID and password, not the hotel network name or access password.

Is there any way this can be accomplished? If not, I will have to return this device.