If it's set to Away from Familiar Locations: Continue to tap Try Again when prompted with Face ID, until you can enter your passcode, thus starting the 1 hour delay to turn it off.
If it's set to Always: Sign onto iCloud.com/find, select your iPhone from the list of devices, remove from Account. This turns off Find My and alongside SDP. Then, turn Find My back on but leave SDP off. You may also need to erase your iPhone.
Then get Face ID fixed at your nearest Apple Store Genius Bar or Apple Authorized Service Provider:
Genius Bar Reservation and Apple Support Options - Apple