Some content within Xeros doesn't function well without the Java Development Kit, or JDK. Downloading and installing this will prevent crashes and freezes in a few places, but most predominantly within Raids.
As of this post, JDK 14 is the latest release and doesn't require a sign up to Oracle to download. JDK is completely safe and an officially released product by Java and Oracle. It allows developers to create Java programs and execute and run them much more efficiently. Xeros and the majority of RSPS use JDK religously.
All that is needed to be done is:
Download JDK from the official link: https://www.oracle.com/java/technologies/javase-jdk14-downloads.html
Scroll down and select the download for the installer that best suits your operating system. Most common will be Windows x64 Installer
Open the download and install JDK. This will only take a few minutes
Reboot your PC, and re-open Xeros
Hopefully this will help you to many more Rare Raids Keys, enjoy!