Track recording frequently doesn't work

I've been using the Locus Map Android app for nearly 4 years and it's been fine, but just recently I've found that when I ask it to start track recording, it often doesn't. The distance walked stays at zero and no red line appears on the map.

Often I can get it to work by quitting the app and starting again, or failing that, rebooting my phone. But something seems to have changed recently that makes the track recording unreliable.

Once it starts recording, then it continues recording without problems. It's just getting it started that's the problem.

I'm using version 4.29.0 on Android 11.

Any ideas?