White bars on watch face

That would most likely be a hardware issue with the digitizer in the watch screen.

Let's try a Forced Restart, but if it doesn't fix this, you'll need to schedule an appointment at your Apple Store Genius Bar. Series 4 is a pretty old watch at this point. If it requires an out of warranty replacement, I'd be more inclined to not pay the price and instead invest the money in a newer, more modern Apple Watch.

To Force Restart your watch, press and hold BOTH the digital crown and side power buttons in at the SAME TIME. Keep holding both buttons in for however long it takes for the screen to go dark and keep holding until you see the Apple Logo. When the Apple Logo appears, let go of both buttons and wait till you see the enter your passcode screen to appear, then sign back with your Passcode.

I left both our watches at an Apple Store for them to investigate. Unlink profile, restore to factory setting and set up as a new watch (do not use iCloud back up) - I have to say that this looks to have worked. My son’s watch had a constant white bar and it’s gone. My watch had intermittent white bars and so far they’ve not returned.

So give this a go, it might work for you too. If there was a glitch/bug in an earlier iOS upgrade, this resolves the issue as resetting the watch forces it to the latest iOS version.

Even replacing it with an SE2022 would give a much better Watch for less money than having a Series 4 repaired.

I agree with lobsterghost1, it is hardware.

Hardware can fail following the stress of an update, but probably only weeks before it would have failed and Apple would not compensate for it

First try restart of watch and phone.

If no better, unpair it and set up as new watch.

Add the face back.

No, I don't have any other suggestions. As I said, it's clear if the Forced Restart didn't work, there is a hardware issue with your watch. You'll need to take to Apple for evaluation and it's going to cost money to either fix it (I wouldn't fix it) or buy a new watch (this is what I would do, personally). Watches are subjected to a lots of movement and dings. It's a little computer you wear on your wrist and anything can go wrong at some point.

Both mine and my son’s SE watches have had these white bars appear in the last month. Bought my sons in Dec-22 and mine in Jan-23, so I’m taking them both back to Apple next week. Seeing as they’re barely a year and half old, they’d better offer replacements. The bars come and go, so not there all the time.

You're welcome and good luck.

My AW has the same line. Were you able to fix it - if so how?