OnlyKey Duo stays unlocked even after power cycle

Update: Found out this is actually a feature if a device PIN is not set (source).

My new OnlyKey Duo seems to stay unlocked all the time, even after I remove it from the USB port and plug it in again, or after I plug it into another device. This can’t be the expected behaviour, right? (My non-Duo OnlyKey certainly doesn’t behave this way.)

Software versions:

  • OnlyKey Duo firmware: v3.0.1-prodn
  • OnlyKey App (Windows): v5.3.6

I have set up this OnlyKey Duo as follows:

  • Factory reset on the OnlyKey Duo.
  • Set backup passphrase to the same as my working non-Duo OnlyKey.
  • Created a fresh backup of my non-Duo OnlyKey.
  • Restored this backup to my OnlyKey Duo.