FULL PRODUCT VERSION :
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Darwin xx 16.7.0 Darwin Kernel Version 16.7.0: Thu Jun 15 17:36:27 PDT 2017; root:xnu-3789.70.16~2/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
jrunscript

a=new java.util.ArrayList();
a.add({x:1});

b=a.toArray();

c=Java.from(b);
c[0] instanceof Object; // false, it is ScriptObjectMirror

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
jrunscript

a=new java.util.ArrayList();
a.add({x:1});

b=a.toArray();

c=Java.from(b);
c[0] instanceof Object;


REPRODUCIBILITY :
This bug can be reproduced always.