I think I've found a bug in the meta avatars sdk version 17.2. After calling LoadUser() on an avatar entity that has already been loaded before(which may happen if you'd want to update an avatar's look), the transforms Joint Head, Joint LeftHandWrist and Joint RightHandWrist stop being in the correct positions and simply fix themselves at 0, 0, 0. Here are the steps to reproduce it:
Ensure you have UseStandalonePlatform checked in your OculusPlatformSettings so that your own avatar loads.
Connect your headset with Quest Link and run the scene to let your avatar load.
In the hierachy see how the Joint Head is in the correct place.
Now manually call LoadUser() and see how Joint Head is no longer in the correct place.