So my Apple Watch Ultra was stuck in max brightness. This meant that when I was in bed in a dark room the Watch will still be in max brightness. This was both annoying (as the Watch is too bright at max brightness in a dark room) and that my battery would be drained faster. After taking the Watch to an Apple Store they run diagnostics on it and they found that both the ambient light sensor and compass sensors failed the diagnostics test. Apple is going to replace the Watch under warranty. So if you have this problem I suggest you take the Watch to an Apple store. Thanks