Lock Screen keeps changing on its own.

Hello there,

To help us get a better understanding of the issue, we’d like to ask a few questions.

1. When this happens, do you receive any errors or messages on your device? If so, what does the error say?

2. Does this happen with all wallpapers, or just those specific ones?

3. You mentioned that the issue started after updating; to confirm is your device running 16.4.1 at this time?

The above details will help us plan how to proceed.

Please also check out this link, and ensure the correct process to change your iPhone Lock Screen is being used, so we can make sure there's no issue there: Change your iPhone Lock Screen

Edit your custom Lock Screen

After you create a custom Lock Screen, you can make changes to it.

1. Touch and hold the Lock Screen until the Customize button appears at the bottom of the screen.

2. Swipe to the Lock Screen you want to edit, then tap .

3. Do any of the following: 

* Choose a wallpaper: Tap an option in one of the categories (for example, Featured, Suggested Photos, or Photo Shuffle) or tap a button at the top of the screen (Photos, People, Photo Shuffle, Emoji, or Weather). If you want to add a photo to your Lock Screen, see Customize your Lock Screen photo.

* Add widgets: Tap the box below the time (or the date above the time), then tap the widgets you want to add.

* Select a photo style for a Lock Screen with a photo: Swipe to change the color filter (for example, Vibrant, Tone, Deep, and Vapor), the background for the photo (Natural, Black & White, Duotone, Color Wash, and so on), and the font for the time.

* Add a multilayered effect for a Lock Screen with a photo: Tap  at the bottom right, then choose Depth Effect (not available for all photos).

* Change the Focus: Tap Focus near the bottom of the wallpaper, then choose another Focus from the list.

* Change the style of the time: Tap Customize, tap the time, then select a font, color, and shade by tapping .

Note: You can also add new wallpaper in Settings .

Thanks!