After some research it looks like it often happens with ren'py game, I have no definitive fix, but one worked for me, you have to use the latest update with this update of the renpy plugin https://www.patreon.com/posts/joiplay-1-20-032-85460458
It's from the joiplay patreon. It worked on my mobile phone since I develop the game with Ren'py 8.1 it needs one of the most recent update of the ren'py plugin to work, please try this.