JSON Requests failing in Wordpress via PHP Script - php

Question

I have been having trouble with a HTTP-GET request rendering consistently on my Wordpress site. Below is the 3rd party PHP script that is being used for the GET request. I don't have any experience with PHP, and I would like to ask the community if everything seems sounds in the code below.
I checked for syntax errors already, and as noted above, the code functions, just not always. I have spent hours on the phone with my hosting provider who says its not them, hours on the phone with my web dev team who says its not them, and all my testing of my API is showing it works from various sources (Postman, browser, c# request).
What I know:
- The API does NOT paginate data unfortunately, which was believed to be the main issue at first. But now were seeing this issue with requests as small as < 50KB. Requests can contain thousands of rows, which can increase the response size to ~2MB.
- The hosting provider has ruled out any timeouts, which is set at 60 seconds. Most responses are processed and returned from my endpoint within 2-5 seconds.
Update 1: Team is testing PHP functionality in another host to eliminate the possibility of environmental host issues.
Update 2: Hosting environment seems to be responsible for the issues with not rendering the data appropriately.
Update 3: Still haven't found the root cause. Closing question with no answer.
Script:
<?php
$request_url = "[endpoint_url]&PortalId=".$_GET['PortalId']."&StartDate=".$_GET['StartDate']."&EndDate=".$_GET['EndDate']."&Location=".$_GET['Location']."&County=".$_GET['County']."&LastName=".$_GET['LastName']."&FirstName=".$_GET['FirstName'];
$jrequest = file_get_contents( $request_url );
if( $jrequest ) {
$jsondata = json_decode($jrequest, true);
if( ! empty( $jsondata ) ) {
$success=1;
$totaljsondata = count($jsondata);
};
};
?>