Update: I can also reproduce this on an iPhone 13 mini running iOS 26.x (Geometry Dash). The frame rate drops whenever the Volume HUD is visible and recovers once it fades out. So this isn't specific to iOS 27, to the iPhone 11 Pro, or to battery health. It affects at least iPhone 11 Pro (iOS 27.2) and iPhone 13 mini (iOS 26).

I can confirm this on a different device. iPhone 11 Pro (original battery, 80% health), iOS 27.2. Whenever the Volume HUD is visible during gameplay, frame rate drops to around 20 FPS in 60 FPS games (reproduced in Geometry Dash and Terraria, so it's not game-specific). FPS returns to normal as soon as the HUD fades out. Notes: • Low Power Mode used to mask the issue, but no longer does. • Screen Recording masks the issue. • Reduce Transparency does not help. • Adjusting volume via Control Center avoids the problem. This looks like a system compositor issue rather than a game issue. Has anyone found a fix?