Special characters in WiFi password

[BeoQ]

Hi all,

Problem Description:
Is use Special Characters (like +-!§$%&/=?_:;) in the password for my WiFi network.
I was unable to to connect. Even using quotes or escape sequences or html-style encoding did not work.
Neither in the MKS-WiFi's AP-webinterface, nor when using the config file on the SD-card.
Searching for 'special characters' in MKS on github did not bring helpful results.

I have worked around the problem by setting up an additional WiFi network with a different password only for this.
This works, and is proof that the basic setup is ok, but I found it causes intermittent dropouts on my main WiFi, so I'd like to remove it. Changing the password in my main WiFi net is not an option.

Question/Issue:
How to enter a WiFi password that has special characters in it?
i.e: Do i need a very special encoding, or is it a bug in the firmware?
Especially, if the first character is special?

My Setup:
MKS Robin WiFi 1.1 module on an MKS Robin Nano 1.x board.
Used in a Q5 Delta printer, with Flsun's mks-derived standard firmware v2.5 from Jan-2021.

Even though the board firmware is not vanilla MKS firmware, it correctly loaded the WiFi firmware file from SD to the Module, using MKS Robin WiFi FW 1.0.4; it shows the WiFi screen on the TFT and displays whatever credentials i had set in the config file, but without special characters.
When accessing the WiFi config using the built-in AP, it shows the same behavior, but the board is not concerned.

In my understanding, the problem is located within the WiFi firmware.
I have some decades in understanding electronics, but my programming skills are not sufficient to track down this issue in the code and fix it myself.

Additional:
What additional information would be helpful?
I can test using the webinterface of the config file.
I can test flashing firmwares thru webinterface or SD-Card.
I may be able to compile a custom firmware using arduino ide, untried yet.

Thanks,
Flo