Vungle Ads Black Screen Bugs

Since few days I suffer from Black screen freeze when watching a ads. Its not really a big huge bugs because I still get my reward but still a little annoying to close and reopen the game each time I watch a ads

PS : interesting not happen always. I just rewatch a video (no clue why a another video was available i feel like I have gain 2 chests in a row) and the video was ok. So its seem random