F5 ASM custom response page issue

Hi all. In our implementation we have 2 ASM policies associated with 2 separate virtual servers. A custom response page (asm blocking page) has been created for the 1st policy where html code is hosted on F5 asking for icons and paths back to the application. Once we set a custom response page (html code) for our 2nd policy then the content of the first one appears corrupted with no images except from the text. Everything comes back to normal and the issue disappears when we set the F5's Default response page on the second policy. Has anyone ever experienced anything similar ? The version we are running at the moment is 13.1.0.0.0.1868 but we couldn't find any fixes regarding this on the follow up releases. Can anyone help with the scenario described above? Thanks in advance