Unable to serialise error

I have a fresh installation of Magento2.3.4 and i have been getting this unable to serialise error and i don’t know what to do with it.

analytics_updateError   Unable to unserialize value. Error: Syntax error

I have tried to add is_serialized() function at
vendor/magento/framework/Serialize/Serializer/Json.php but it has not resolved .this is the code below which i added

public function unserialize($string)
    {
        /* Added this code to resolve the issue */
        if($this->is_serialized($string)){
           $string = $this->serialize($string);
        }
    /*---------------------------------*/
        $result = json_decode($string, true);
        if (json_last_error() !== JSON_ERROR_NONE) {
         throw new InvalidArgumentException('Unable to unserialize value.');
        }
        return $result;
    }

function is_serialized($value, &$result = null)
    {
    // Bit of a give away this one
    if (!is_string($value)) {
        return false;
    }
    // Serialized false, return true. unserialize() returns false on an
    // invalid string or it could return false if the string is serialized
    // false, eliminate that possibility.
    if ($value === 'b:0;') {
        $result = false;
        return true;
    }
    $length = strlen($value);
    $end = '';
    switch ($value[0]) {
        case 's':
            if ($value[$length - 2] !== '"') {
                return false;
            }
        case 'b':
        case 'i':
        case 'd':
            // This looks odd but it is quicker than isset()ing
            $end .= ';';
        case 'a':
        case 'O':
            $end .= '}';
            if ($value[1] !== ':') {
                return false;
            }
            switch ($value[2]) {
                case 0:
                case 1:
                case 2:
                case 3:
                case 4:
                case 5:
                case 6:
                case 7:
                case 8:
                case 9:
                    break;
                default:
                    return false;
            }
        case 'N':
            $end .= ';';
            if ($value[$length - 1] !== $end[0]) {
                return false;
            }
            break;
        default:
            return false;
    }
    if (($result = @unserialize($value)) === false) {
        $result = null;
        return false;
    }
    return true;
}

Any help here would be much appreciated

thanks
Harish