I'm setting up some devices with a custom rom and my own custom app zip. Generally it works fine but I've found that some apps misbehave when installed into the system partition. What usually happens is that the app starts successfully but later crashes or just refuses to work properly.
Why would an app work properly with installed to
/data but not when installed to
The apk files are installed to
/system/priv-app and their libraries are unpacked into
(hopefully irrelevant to the question but the device in question is Amazon Fire KFFOWI with ResurrectionRemix custom rom which is Android 5.1.1).