WoW Version

Retail, since 10.2 release.

Describe the bug

View port seems to not work correctly for me? I've originally set the top VP by 55. When I set that number to 0, nothing happens. If I set it back to 55, it changes to what it should be set to. This effect sometimes happens during dungeons and raids (and outdoor world quest cinematics). When I reload UI, it'll go back to the state of 0 but with it set to 55.

Any ideas why this happens?

Seeing this as well, apparently viewport is no longer applied on reloadui recently.