Build fails with app:transformClassesAndResourcesWithProguardForRelease

Had similar problem,

-ignorewarnings

At the end of proguard-rules.pro fixed it.

A similar issue is referenced here. It seems to be fixed in proguard 5.3.3.

Try upgrading proguard to 5.3.3 with :

buildscript {
    configurations.all {
        resolutionStrategy {
            force 'net.sf.proguard:proguard-gradle:5.3.3'
        }
    }
}