Gotcha! Thank you for the information, once again. ^^
I'll double check with our engine programmer to see if there's anything that comes to mind to try for fixes. I believe this very issue was brought up with v0.17 a while ago too and we thought it was linked to a newer version of Ren'py software that was downloaded during v0.17 development, but it doesn't seem that way since we went back to a more stable Ren'py update during v0.18 to test that.
(Joys of mobile testing troubleshooting! ^^")
The link below should take you to a publicly open post made on our Patreon. Inside the post there's 3 links for Windows, Mac, Android for v0.18 to be downloaded through MEGA. If you'd like to try that and hopefully it'll help, otherwise we'll keep notes and continue to do some research around as to what might be causing issues.
https://www.patreon.com/posts/53311076