Apple Watch Alarm Making Noise in Silent Mode

I have an apple watch that I like to use as a "silent alarm" in the morning. I have an alarm set to wake me up, but the watch is set to silent mode so it will vibrate without any noise. Most of the time, this works perfectly. However, the watch has started to mysteriously slip out of silent mode, and make noise along with the vibrations when the alarm goes off. To make matters even more confusing, it is not consistent. It doesn't happen every day and when it does happen, if I hit the snooze button, the alarm will vibrate without sound (as I intended) the next time it comes on.

This is driving my partner crazy. The whole point was to have an alarm to wake me up that allowed everyone else to sleep. I even prefer the sound-less wake up. I have scoured the internet looking for other people experiencing the same issue, but this is the first time I am posting about it. Does anyone have any ideas about why my watch would ignore silent mode?

Thanks!