LSLB 503 detection
 

So I am have been running into an issue where LSLB thinks the backend servers are down, I believe it is because the ping url is not working quite right.

The log shows:
Failure detected: Unexpected status code, 0:Success

for both webservers, they are cpanel servers so I am using URLs like:
http://68.235.35.003:80/~adz

However after that the logs show:
[27.248.10.65:5258-0#adzmedia.com] External processor is not available!

eventhough both servers are responding normally.

It does not do that when the /~adz part is removed, but then it is only checking the cpanel default page, not the page for the website.

I assuming you have multiple vhosts setup on backend webserver. with direct IP access, default page is expected.