The issue is that your output contract has two item's in the items array. This is an array of strings, so you only need to have one string configured in the items array, which will allow any number of strings to be returned in that array.
"Data returned to a script from a data action must be in a compatible format. Currently, scripts cannot read data from a JSON array. Some fields returned from Data Dip connectors may currently be inaccessible."
I'd still be interested in if I can pass all the data into one string eg: ("string1, string1")