MR Controllers not correctly named, refuse Bluetooth connection

Both controllers show up in the Bluetooth device list as "Input (Input)", and they are seen as game controllers. My phone interestingly sees them both correct with their "Left" and "Right" names. The PC refuses to connect ("device doesn't reply") and the full MR headset setup process does also not find the controllers (surely because the names are detected wrongly).
The headset otherwise works fine (tracking/visuals).

I tried everything suggested in Troubleshooting so far:
- reset controllers to factory
- update bt drivers (it's a Qualcomm onboard)
- restart & wait & restart etc.
- bt troubleshooting
- the Troubleshooting Controllers flowchart unfortunately doesn't show what "Step A.. H" are.
- full MR uninstall and reinstall

Any ideas?