Error when trying to update plugin

[northernbeacheswebsites]

Everything seems to be working ok except for the final step of actually updating the plugin.

When I try clicking the update button I get the following error:

Update Failed: The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature

I have done a bit of Googling on this error message and it's commonly associated with bad zip files or not enough server resources but I am very very confident this isn't the issue in my case because I have tried my own plugins and also existing well established plugins like Akismet and they all get the same error. I have also tried running the updates on my local server (MAMP) and on a typical live Apache server and they are all getting the same error message.

As you know from my previous issue I am running this as a plugin. My plugins code is blank it's not checking for anything so the download should just work. Here is a metadata url:

https://northernbeacheswebsites.com.au/?update_action=get_metadata&update_slug=akismet

and my plugin code is like follows:

<?php
/*
Plugin Name: Plugin Update Server
Description: An example plugin that runs the update API.
Version: 1.0
Author: Yahnis Elsts
Author URI: http://w-shadow.com/
*/

require_once __DIR__ . '/wp-update-server/loader.php';

class ExamplePlugin {
	protected $updateServer;

	public function __construct() {
		$this->updateServer = new MyCustomServer(home_url('/'));
		
		//The "action" and "slug" query parameters are often used by the WordPress core
		//or other plugins, so lets use different parameter names to avoid conflict.
		add_filter('query_vars', array($this, 'addQueryVariables'));
		add_action('template_redirect', array($this, 'handleUpdateApiRequest'));
	}
	
	public function addQueryVariables($queryVariables) {
		$queryVariables = array_merge($queryVariables, array(
			'update_action',
			'update_slug',
		));
		return $queryVariables;
	}
	
	public function handleUpdateApiRequest() {
		if ( get_query_var('update_action') ) {
			$this->updateServer->handleRequest(array_merge($_GET, array(
				'action' => get_query_var('update_action'),
				'slug'   => get_query_var('update_slug'),
			)));
		}
	}
}

class MyCustomServer extends Wpup_UpdateServer {

}

$examplePlugin = new ExamplePlugin();

Do you know why this error may be occurring? Thanks,

[YahnisElsts]

I tried to manually download the update and got the site homepage instead of a ZIP file. It looks like this is because download_url still has the old query parameters action and slug where it should have update_action and update_slug. To fix that, you'll need to override the generateDownloadUrl method as shown in the "Running the server from another script" example:

protected function generateDownloadUrl(Wpup_Package $package) {
    $query = array(
        'update_action' => 'download',
        'update_slug' => $package->slug,
    );
    return self::addQueryArg($query, $this->serverUrl);
}

[northernbeacheswebsites]

Ahh thanks so much, I must have somehow removed this from my code. Everything is up and running now so I won't bother you any more. Your plugin and assistance have been fantastic, I really appreciate it.