Mine was set to 5 second interval. It stopped after tracking 2 points only. I didn't do anything with phone between starting track and end, other than putting in phone and it auto-locked. ( Holster lock ). Last time it tracked 46 points while being in locked mode, so that shouldn't be the problem.

I checked the log and the story is same. The log ended with entries with Startapp and Pauseapp, with 9 seconds between those 2 entries.

I will test with 15 second interval now.

*edit*
It stopped after 6 points. Log entry, other than usual info, just shows "(time) a Starting locationLister with interval 15". When I return to main screen, the "Tracking" box at top right appears again, but after 15 seconds disappears with no new point at all. I waited quite a bit, but still no new points.