iPhone XS crashing and battery failing falling 5-10 maximum capacity each time

First things first. Get the battery replaced as soon as you can. The Apple technician will run checks and tests on the iPhone at the time that the battery is replaced.

Normally, Apple will not replace the battery unless it is under 80%, but they may make an exception since you are having battery related problems.

Make sure that the you have the battery replaced at the Apple Store or an authorized Apple service shop. You can find a list of authorized shops in your area using this link:

Find Locations

First things first. Get the battery replaced as soon as you can. The Apple technician will run checks and tests on the iPhone at the time that the battery is replaced to make sure that all systems are go.

It would not hurt to do a Forced Restart if you have not done this recently, but I doubt it will help.

Force restart iPhone - Apple Support

Normally, Apple will not replace the battery unless it is under 80%, but they may make an exception since you are having battery related problems.

Make sure that the you have the battery replaced at the Apple Store or an authorized Apple service shop. You can find a list of authorized shops in your area using this link:

Find Locations

Are you able to see the Maximum Capacity reading on the iPhone? If yes, what is it?

If it is less than 80%, the battery needs to be replaced immediately.

Settings > Battery > Battery Health & Charging > Maximum Capacity.

If you are not able to see the Maximum Capacity setting on the the battery about when was the last time that you replaced the battery in the iPhone?