iphone8 after 15.5 update issues

After taking the 15.5 update on my wifes iphone The start up screen is white with a black apple, battery drains very quickly. I backed it up via icliod & did a recovery/restore from icloud, it did not clear up these issues. I have the same phone and do not have this problem.

Seems there are no easy fixes for this. I did take it to Best But and the tech there ran tests. It said there was a battery issue, but did not recommend a new battery.

Phone will still work after it shuts down because of low battery if I use the power cable.

I am out options.

Any comments welcome