You can find out the following from ejs console:
Caused by: java.lang.ArrayIndexOutOfBoundsException: -1
at users.lookang.weexvav17rebuildworkingold_pkg.weexvav17rebuildworkingold._method_for_showcoordinates_l2_y(weexvav17rebuildworkingold.java:624)

Open weexvav17rebuildworkingold.java (under output directory) check out line 624:
which is:
 public double _method_for_showcoordinates_l2_y () { return yv[j]; }

The problem is due to j has been assign a value which is not acceptable: for example: -1

for example: you assign Element property to j in ParticleSet_movable2
which mean that j will be assign value -1 when mouse is not move to those particles (not selected).
You might have other setting cause similar effect.

You can change the setting from yv[j]  to yv[jid]: and defind a new variable jid
add the following code at "Fixed Relation page)
if(j>-1 && j<n)jid=j;
else jid=0;// or other valid values.