Script Snap Error: "[object JavaPackage] is not a Java class in nashorn:mozilla_compat.js"

I have a script snap that I’m using to do some weird data manipulation to amalgamate 3-hourly data and 1-hourly data into a consistent 1-hourly format. Here is my script, I’m using javascript code:

// Ensure compatibility with both JDK 7 and 8 JSR-223 Script Engines
try { load("nashorn:mozilla_compat.js"); } catch (e) { }

// Import the interface required by the Script snap.
importPackage(com.snaplogic.scripting.language);

// Import the serializable Java type we'll use for the output data.
importClass(java.util.Array);

/**
 * Create an object that implements the methods defined by the "ScriptHook"
 * interface.  We'll be passing this object to the constructor for the
 * ScriptHook interface.
 */
var impl = {
    /*
     * These variables (input, output, error, log) are defined by the
     * ExecuteScript snap when evaluating this script.
     */
    input: input,
    output: output,
    error: error,
    log: log,

    /**
     * The "execute()" method is called once when the pipeline is started
     * and allowed to process its inputs or just send data to its outputs.
     *
     * Exceptions are automatically caught and sent to the error view.
     */
    execute: function () {
        this.log.info("Executing Transform Script");
        while (this.input.hasNext()) {
            try {
                // Read the next input document, store it a new LinkedHashMap, and write this as an output document.
                // We must use a serializable Java type liked LinkedHashMap for each output instead of a native
                // JavaScript object so that downstream Snaps like Copy can process it correctly.
                var inDoc = this.input.next();
                var outDoc = new Array();

                var earliestTime = new Date(inDoc.original.start_date);
                var latestTime = new Date(inDoc.original.end_date);

                var forecasts = [];
                for (var i = 0; i < inDoc.entity.forecasts.arrayLength; i++) {
                    var forecast = inDoc.entity.forecasts[i];
                    forecast.validFromDate = new Date(forecast.validFrom);
                    forecast.validUntilDate = new Date(forecast.validUntil);
                    forecasts.push(forecast);
                }

                var checkingTime = earliestTime;
                do {
                    var outputObj = {
                        weatherDate: checkingTime,
                        weatherData: {}
                    };

                    var validPt0s = {};
                    var validPt1h = {};
                    var validPt3h = {};

                    for (var i = 0; i < forecasts.arrayLength; i++) {
                        var forecast = forcasts[i];
                        if (forecast.validFromDate <= checkingTime && forecast.validUntilDate >= checkingTime) {
                            // 1) get the first valid PT0S result
                            if (forecast.validPeriod === "PT0S" && !validPt0s) {
                                validPt0s = forecast;
                                outputObj.weatherData.airTemperatureInCelsius = validPt0s.airTemperatureInCelsius;
                                continue;
                            }
                            // 2) get the first valid PT1H result
                            if (forecast.validPeriod === "PT1H" && !validPt1h) {
                                validPt1h = forecast;
                                outputObj.weatherData.precipitationAmountInMillimeter = validPt1h.precipitationAmountInMillimeter;
                                outputObj.weatherData.netRadiationInJoulePerCentimeterSquare = validPt1h.netRadiationInJoulePerCentimeterSquare;
                                continue;
                            }
                            // 3) get the first valid PT3H result
                            if (forecast.validPeriod === "PT3H" && !validPt3h) {
                                validPt3h = forecast;
                                outputObj.weatherData.averageWindSpeedInKnots = validPt3h.averageWindSpeedInKnots;
                                continue;
                            }
                        }
                    }

                    outDoc.push(outputObj);
                    checkingTime.setMinutes(checkingTime.getMinutes() + 60);
                }
                while (checkingTime <= latestTime)

                this.output.write(inDoc, outDoc);
            }
            catch (err) {
                var errDoc = new LinkedHashMap();
                errDoc.put("error", err);
                this.log.error(err);
                this.error.write(errDoc);
            }
        }
        this.log.info("Script executed");
    },

    /**
     * The "cleanup()" method is called after the snap has exited the execute() method
     */
    cleanup: function () {
        this.log.info("Cleaning up")
    }
};

/**
 * The Script Snap will look for a ScriptHook object in the "hook"
 * variable.  The snap will then call the hook's "execute" method.
 */
var hook = new com.snaplogic.scripting.language.ScriptHook(impl);

The error I’m seeing is:

Failure: Cannot evaluate Script file: <WHOLE SCRIPT HERE>, Reason: TypeError: [object JavaPackage] is not a Java class in nashorn:mozilla_compat.js at line number 375 at column number 16, Resolution: Please fix the script file error at line: 375 column: 16

Since the error is pointing somewhere other than my code, is there something that needs to be installed on our own workers? Is this just a misleading error and there is something wrong with my script? I used the boilerplate code as a template so am pretty sure that nashorn:mozilla_compat.js is the right thing to use.

Edit: Here is some input json you should be able to use to reproduce.

[
    {
        "entity": {
            "forecasts": [
                {
                    "validFrom": "2021-03-01T00:00:00Z",
                    "validUntil": "2021-03-01T00:00:00Z",
                    "validPeriod": "PT0S",
                    "airTemperatureInCelsius": 2.0
                },
                {
                    "validFrom": "2021-02-28T23:00:00Z",
                    "validUntil": "2021-03-01T00:00:00Z",
                    "validPeriod": "PT1H",
                    "precipitationAmountInMillimeter": 0.0,
                    "netRadiationInJoulePerCentimeterSquare": -9.8
                },
                {
                    "validFrom": "2021-02-28T21:00:00Z",
                    "validUntil": "2021-03-01T00:00:00Z",
                    "validPeriod": "PT3H",
                    "averageWindSpeedInKnots": 5.1
                },
                {
                    "validFrom": "2021-03-01T01:00:00Z",
                    "validUntil": "2021-03-01T01:00:00Z",
                    "validPeriod": "PT0S",
                    "airTemperatureInCelsius": 1.7
                },
                {
                    "validFrom": "2021-03-01T00:00:00Z",
                    "validUntil": "2021-03-01T01:00:00Z",
                    "validPeriod": "PT1H",
                    "precipitationAmountInMillimeter": 0.0,
                    "netRadiationInJoulePerCentimeterSquare": -7.1
                }
            ]
        },
        "original": {
            "start_date": "2021-03-01T00:00:00.000Z",
            "end_date": "2021-03-01T01:00:00.000Z"
        }
    }
]