Though I when last changed countries I did find that I lost some purchases. I would guess it can happen when an item is not available in the new country.

There’s a rate limit on how often you change countries and you’ll need a payment method from the country you want to change to (e.g. a credit card issued in that country, the address on the card doesn’t matter).

You’ll also need to cancel e.g. your Apple TV+ subscription before you can switch.