my watch keeps shutting down spontaneously, which is quite infuriating.

8756111 said:

How can I salvage this situation?

If you like the design of the watch, I recommend exchanging it for Instinct 2. It does not suffer from these problems, and it is way (light years) better watch, with many more features than the old Instinct. If you can afford it, get rather the 2X model.

Cheers mate, but I want to salvage these watches specifically. Where can I find the installation program for version 17.50?

Until now, as far as I remember, nobody reported back, here on the forum, that the downgrading of the firmware helped to solve the problems with crashes, hence the recommendation to exchange the watch for I2 while you still can. Since you wrote you purchased it just a few days ago, you should still be able to exchange it, but you may lose that possibility if you wait too long.

v17.50 is for example in the rollback folder of the side-load package for the beta v18.41. Originally it was posted here: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/instinct-solar/311093/instinct-solar---18-41-public-beta but the download link seems to be dead. You will have to google for it, or get it from a fellow user who kept the beta package.