Yeah, this is unfortunately a bit of a bug with the Android build, which I will be rectifying ASAP. Tom (the creator of Ren'Py) has advised that the latest version of Ren'Py should fix this issue, and I will be releasing an update soon with this fix. Think of this future version as 6.5.1.
The unfortunate part is that I don't have an Android device myself. My family do, but they'd object to me using their devices as test subjects.