Fairphone 4 torch switches off by itself

My fairphone torch has suddenly started switching itself off. Sometimes it will do this in as little as 10 seconds, other times it stays on longer before doing so. The torch button goes off at the same time. I couldn’t find any configuration for this, so I’m puzzled why it’s doing it. Battery is well charged (80%), and with a good capacity (was new 9 months ago).

Any ideas?