You are an absolute saint for this! I've been trying for weeks to get an working Android Build!
This is a quick and simple method to help you port your RPG Maker game to Android · By
I'm using MV. It turns out the battle issue was caused by a plugin, EnemyActor, not working. I'm getting a similar issue when changing options in the options menu and when trying to save. I'm planning to debug it this weekend. If you want I can send the apk or the file with my assets if you want to check it out too.
Okay then. It is easier with newer versions. The issues are likely about some safety stuff as far as I can see. Althou it doesn't seems that at first glance.
I mean, it is more about the plugins. I made it with a good amount of plugins but I tested all them before build the final APK. I had to replace some of them due some js errors. So yeah it depends on how the plugins are made. Some works just fine others doesn't so much