I'm seeing this at least when I load scripts from another - I refer to these as subscripts. My usual pattern is to wrap all the code in there into a class, such as:

class FooSubScript{

    final def steps

    FooSubScript(steps) {
        this.steps = steps
    }
....

I've only recently started doing this, to better share code between several scripts. The pattern has been working over the last few weeks but suddenly stopped working, I believe yesterday. I get errors along the lines of:

groovy.lang.ReadOnlyPropertyException: Cannot set readonly property: globals for class: setupSubScript
at groovy.lang.MetaClassImpl.setProperty(MetaClassImpl.java:2744)
at groovy.lang.MetaClassImpl.setProperty(MetaClassImpl.java:3770)
at setupSubScript.setProperty(Script1.groovy)

(in this particular example, the first property was called globals)

As far as I can see that is perfectly valid groovy. Commenting or deleting the final makes it work.