One of the biggest challenges I have faced while developing for VR/AR with Unreal Engine is the lack of documentation and tutorials available. Unreal Engine is a powerful engine, but the lack of tutorials and documentation can make it difficult to learn how to use it effectively. For example, I recently wanted to learn how to create a VR experience in Unreal Engine, but the only resources I could find were a few scattered YouTube videos and some forum posts. This made it difficult to learn the basics of VR development in Unreal Engine, and I had to spend a lot of time experimenting and troubleshooting to figure out how to do what I wanted.