I had the exact same symptoms: tablet thinks its disconnected from keyboard while being stuck attached and the red light staying on all the time. No 'usual' rebooting, bios fixes helped.
In my case it got stuck when I attached the tablet to base while in sleep.
While it got stuck, it did not actually lock in properly, so after some panicky hours I noticed that clipboard would actually lift a bit under serious force. So after trying every single troubleshooting guide/post I could find, I just took a deep breath, closed my eyes and ripped it off!
I noticed there was a smudge on contacts and when I cleaned it off, it started working again.
But again, in my case it wasn't properly locked in so just removing it by force worked.