Apple Watch ringing even when off wrist and locked

Hi. My series 5 Apple Watch, after a software update has started ringing when I receive calls, despite being off my wrist, locked, with wrist detection enabled and updated software installed? It even rings when left at home and me and my iPhone are out of the house! Which scared the wife as she wondered what it was!

The calls can be answered, without unlocking which is very worrying!!! Is this a software bug??