Auto Restart Timer freezes during activity

I've created a timer that auto restarts. When using this timer during an activity it always stops after repeating a few times. I think somewhere around 3-8 times it will stop. If the Sound is on it just keeps beeping whilst the timer has already stopped/frozen. It's super annoying and often leaves me hanging...

My use case is when I'm at the gym there are certain workouts I want to do 10s on, 10s off repeats (for example bridges).

When I use this timer not during an activity, it works completely fine.

Anyone else have this problem?