The following code will fail in non-CPS-transformed sandboxed Groovy, but will pass in CPS-transformed-and-sandboxed Groovy or vanilla Groovy:

def m = [fruitA: 'apple', fruitB: 'banana']

def bKey = 'B'

assert m."fruitB" == m."fruit${bKey}"

That's obviously wrong. Not sure yet where the problem is happening but will dig.