battery not holding charge

What's not suprising is a five y.o. battery not holding a charge. Also, the long process of applying an iOS update to an old iPhone with a weak battery can be the proverbial "straw that broke the camel's back."

...So, you can wait for suggestions from other users here, but I would have that aging, likely weak battery replaced:

iPhone Battery & Power Repair

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

õ¿õ¬

whisperingduck ~ Which model of SE is it?...

iPhone SE (1st generation) released in 2016

iPhone SE (2nd generation) released in 2020

iPhone SE (3rd generation) released in 2022

Settings > General > About > Model Name

õ¿õ¬

Okay, does your iPhone SE 1st gen. still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

õ¿õ¬

85% is suprisingly good for an original battery that's at least 4 years old...

When did you buy this iPhone?

Did you buy it new?

õ¿õ¬