Another victim of this problem. Wrote the official Raspberry Pi 8.0.2 version to a microSD card, had fun at home (including connecting to my wireless network), took the pi to work, tried to connect to the wireless network and got the "Invalid argument" message just after selecting the ESSID and clicking on Connect (no password was asked). Had to resort to a Soft Reset (LibreELEC settings, System, Reset System Settings to Defaults), no trouble in connecting to the network after the Soft Reset reboot.
I am using the Rapberry Pi Zero W, wich has a CYW43438 wireless chip (same as the Raspberry 3). I downloaded the official LIbreELEC 8.0.2 image (LibreELEC-RPi.arm-8.0.2.img.gz), so the developers should know "which crappy wireless driver is involved". If not, give me instructions and I will gather the information. Could not SSH to get logs, as I was could not connect to the network.