Galaxy S25 Ultra Problems After One UI 9: Battery Drain & Fixes

The update finishes, the phone reboots, and instead of your home screen you get a setup page with an XML error that says “Access Denied”. That was the strangest of the Galaxy S25 Ultra problems after One UI 9 arrived. The more common ones are quieter: screen-on time cut in half, a phone that’s warm in standby, and charging that seems slower than it used to be.

Most of it is software and can be fixed at home. A few symptoms are hardware, and for those you want Samsung, not another restart.

Stuck on setup with an “Access Denied” error

After the One UI 9 update installs, some phones boot into the setup screens and stop on an XML “Access Denied” message. Sammy Fans and Android Authority reported it on 12 October 2026 on Galaxy S24, S25 and S26 phones. Android Authority said the affected phones aren’t really bricked, and that Samsung hadn’t confirmed a cause.

What owners say gets them through:

1. Force restart by holding the Side key and Volume Down for about 10 seconds.
2. Boot into Safe Mode. When the Samsung logo appears, hold Volume Down until the phone starts with “Safe mode” in the corner.
3. Take it offline. Turn off Wi-Fi and mobile data. If you can’t get to the settings, pull the SIM or switch off the router.
4. Restart while still offline, finish setup, then reconnect.

Battery drain since One UI 9

One UI 9 is Samsung’s Android 17 skin. According to gHacks, the stable build began rolling out to the Galaxy S25 series, Z Fold 7 and Z Flip 7 in South Korea around 29 September 2026. Android Authority reported on 5 October that US carrier and unlocked S25 models were getting it, with S25-series firmware ending in DZIF and a download of about 3.9GB on the Ultra. Europe and other regions followed in stages. You can see your version in Settings › About phone › Software information, and our One UI 9 rollout tracker has dates by model and region.

The drain complaints followed quickly. Cybernews quoted a Redditor whose screen time dropped from 6–7 hours to about half after the update. Samsung Members threads describe “serious battery drain” on the S25 Ultra.

Part of this is normal after a big Android update. Apps get re-optimised, photos and files are re-scanned, and adaptive battery has to learn your habits again. Sammy Fans suggested it can take around two weeks to settle. Apps that haven’t been updated for Android 17 can also keep the phone awake.

Give it those two weeks with normal charging, then work down this list:

1. Update every app in Galaxy Store and Google Play.
2. Open Settings › Battery › View details. Anything with heavy background use goes into Settings › Battery › Background usage limits › Deep sleeping apps.
3. Turn off Settings › Connections › More connection settings › Nearby device scanning, and location scanning under Settings › Location › Location services, if you don’t use them.
4. Switch off Wireless power sharing in Settings › Battery.
5. Turn off RAM Plus in Settings › Device care › Memory › RAM Plus. It asks for a restart.
6. Wipe the cache partition. Nothing personal is erased. Power off, connect the phone to a PC or a USB-C audio accessory, hold Power and Volume Up until recovery appears, choose Wipe cache partition and reboot.
7. Try Safe Mode by holding the power-off icon until Safe mode appears. If the drain stops there, a downloaded app is responsible.

Hot in your pocket while doing nothing

This started before One UI 9. In July 2026, Tech Advisor reported S25 Ultra owners on the One UI 8.5 update seeing heavy standby drain. One went from 85% to just over 5% in under 12 hours, and phones were getting hot while unused. For some of them, the cause was a WhatsApp backup stuck in the background.

So check WhatsApp first: Settings › Chats › Chat backup. If a backup is stuck, cancel it and run it again on Wi-Fi. Then look at Settings › Battery › View details for any other app with odd background time, and see whether Settings › Device care is offering “Optimise now”.

Restart, and don’t fast charge while gaming or navigating. If the phone is still hot in Safe Mode with every app closed, book a Samsung service check.

Charging slower than 45W

The S25 Ultra supports 45W Super Fast Charging 2.0, but only with a USB PD PPS charger and a 5A-rated cable. Anything less and it quietly charges slower.

• Check Settings › Battery › Charging settings › Fast charging is on.
• Try a Samsung 45W adapter with the cable from the box.
• Clean the USB-C port gently with a wooden toothpick or a soft brush.
• Battery protection holds charging back near the top, and a hot phone charges slower. Both are by design.
• Run Samsung Members › Support › Phone diagnostics to test the cable and battery.

A green or pink line down the screen

A thin vertical line, green, pink or white, that shows in every app, doesn’t appear in screenshots, survives a restart and is still there in Safe Mode is a fault in the AMOLED panel. It isn’t an update bug, and software won’t remove it.

Photograph it, back up, and contact Samsung. A Samsung Info report shows the warranty and country details before you book, and our Samsung IMEI and warranty check article explains what the report shows. On models where Samsung hasn’t disabled it, typing *#0*# in the Phone app opens touch and colour tests.

Going back to One UI 8.5 isn’t an option

Samsung offers no official downgrade. Newer firmware usually raises the bootloader version, which blocks older builds, and flashing old firmware with unofficial tools can fail, trip warranty checks or leave the phone unable to boot. What you can do instead:

• Install the next monthly update. Samsung typically fixes widespread battery and stability bugs in the following security patches. Check Settings › Software update › Download and install every week or so.
• Send Samsung the logs. In Samsung Members › Support › Error reports, attach system logs while the problem is happening. That is how Samsung’s engineers see it.
• Reset as a last resort. Back up with Smart Switch or Samsung Cloud first. A clean start on One UI 9 often clears drain left over from the upgrade. If you plan to sell the phone afterwards, remove your Google and Samsung accounts before the reset.

If the drain is still bad after a reset and a week of normal use, Samsung’s advice to affected owners has been to contact support and book a service appointment, where technicians can test the battery properly.

Buying a renewed or used S25 Ultra

Samsung says Certified Re-Newed Galaxy S24 and S25 models, the S25 Ultra among them, went on sale on Amazon in the US on 21 October 2026. Prices start at $489 for the cheapest model, with a one-year limited warranty and a new battery. Private sales cost less and carry more risk. Before you pay:

1. Get the IMEI from *#06# and run a GSMA blacklist check.
2. Check carrier and SIM-lock status, especially on US carrier models.
3. Confirm the warranty date and country with a Samsung Info S2 report.
4. Go through our used Samsung buying checklist, screen and battery included.