oculus go 360 video lagging

Hi all,working on a application for oculus go. Using a 360 mono video as skybox (4320*2160, 60fps). There's several scenes with a different video in background. The first scene playing smoothly, even if reloaded and reloaded but when I'm loading the second scene, the video is lagging strongly. don't understand why. can someone help me. I did not found an answer :-(