Back button not marking laps


I just go running with my watch to the park, do 2 laps around it and go back home. Therefore I need to press the back button 3 times but it recorded only 2, and I did insist on pressing it several times.

It did show a message like "Recording screenshot of your watch face" once. I did set auto lap OFF and back button ON in the settings. I always use the same activity, the watch is a forerunner 45S, it's new, less than a month and the battery was charged at 80%.

The previous time I went running, I couldn't record any lap at all, I also had the message about screenshot and I realized afterward the settings had strangely been changed: the back button was set to OFF.

Any advice