Honest answer? The export to .apk is done via a thrid party programm and I have exactly 0 knowledge about mobile ports apart from using said programm, so I'll be of little help with such issues that aren't on all systems but limited to android.
Maybe it's related to the android version or phone type, but I can't say for sure. ^^"
I'm currently uploading a new version which will go live later today or tomorrow. Maybe try to download the new version and see if that somehow makes everything work again. XD