This method has been reported to work for various Grundig models and is worth trying before more drastic steps.
I can give you custom steps based on what your unit is doing. Share public link grundig gx-3800 factory reset code
A factory reset completely wipes the internal memory of your head unit. Before you proceed, keep the following in mind: This method has been reported to work for
Scroll down to find the Factory Reset or Initialize option. grundig gx-3800 factory reset code
If the system remains locked or glitched, you may need to download the official firmware package onto a USB drive to flash the system from boot.