Calls from backend servers to other servers are not loading when using LTM

We have a VS configured that connects to a pool of SAP backend servers. These servers make calls to other servers to pull information for forms. About half of the forms are not loading when connecting through the LTM. It looks like the LTM does not like that the backend servers are making calls to other servers by using the server name. To connect to the VS I enter sapportal/ in the browser which redirects the browser to https://sapportal.domain.com/irj/portal. When the form does not load I get the following error, "This page can't be displayed. Make sure the web address is correct".

Is there a way to make it so the calls from the backend servers can pull information from other servers?