Why are there so many short sessions in Analytics and Metrica?

Question

Google Analytics

I am doing analytics for a mobile application and faced the fact that for more than 25% of sessions, the duration is fixed from 1 to 9 seconds. I can't figure out why this is happening or how it works. That is, there are a lot of phantom sessions?
Where do they come from, if any? Well, that is, nothing is clear. I can't find any info on the internet about this. What to do? Maybe one of the colleagues came across and shed light on the mystery?