The problem is caused by a timebomb in the original software.
Over time it will damage random sectors. Your only hope is that damage is at a place that get the radio stuck but is still fixable.
Build or buy a serial interface, solder it to the main board (J4) and go from there.
You probably will discover a crashed OS and/or kernel.. possibly a damaged bootloader.
In case of the OS you might be able to repair it..
If it is the kernel it will be difficult. If the bootloader is crashed you for sure are out of luck.
I am not spending time on these devices anymore as the value of the radios is simply not worth the efforts.
I have created alternative firmware and also a recovery mode that creates a dual boot option which makes it possible to fix crashed devices by SD card.
But ONLY when the ListenLive recovery mode has been installed before the device crashed!