OnChange event erroring on onChange event JS Aras version 12


I have an odd error I have never seen before. I have two drop down fields on one of my forms, lets call them field1 and field2.

Now, both of these fields have on OnChange event attached to them, field1 event triggers the OnChange event on field2. When I trigger the event on on field1 I get this error and neither event fires.

if I remove the OnChange event on field2, re-save the form and trigger the event then it works as suspected minus field2 event firing.

it looks like an OnChange event cannot fire an OnChange event? Has anyone ever seen this? I tried re-making both the forum and JS methods but it doesn't seem to do anything.

Spec: (Free version of innovator on Aras webpage) 

Aras Innovator Version 12.0  Build: 13341

MS Build Number: 000000.00