Errors when I try to save a page that uses the PHP Code snippet

Hello!

Sometimes I get this error:
E_ERROR was caused by line 3 of the file /wp-content/plugins/insert-php-code-snippet/shortcode-handler.php(99) : eval()’d code. Error: Cannot redeclare getWaterLevel() (previously declared in /wp-content/plugins/insert-php-code-snippet/shortcode-handler.php(99) : eval()’d code:3)

Here is the code I try to insert:

<?php

function getWaterLevel($data, $stationName) {
    foreach ($data as $entry) {
        if ($entry->Station == $stationName) {
            return $entry->{'Water Level (cm)'};
        }
    }
    return null;
}

// The URL containing the JSON data
$url = "https://example.com/water_data.json";

// Use file_get_contents to fetch the contents of the URL
$response = file_get_contents($url);

// Check if the request was successful
if ($response !== false) {
    // Use json_decode to parse the JSON data into a PHP object
    $data = json_decode($response);
    
    if ($data !== null) {
        // Test the function
        $stationName = "SomeStation";
        $waterLevel = getWaterLevel($data, $stationName);
        
        // Print the result
        echo  $waterLevel;
    } else {
        // Print an error if the JSON could not be parsed
        echo "Error: Could not parse JSON data.";
    }
} else {
    // Print an error if the request was unsuccessful
    echo "Error: Could not fetch data from the URL.";
}

?>

What could cause this?
I have to delete the autosaved version in wp_post table in order to be able to open and edit the page!

Kind Regards!