Like stated, I have noticed that I would log back in the game and the inventory I sorted my previous logging was not saved (it reverted to what it was before sorting). This has started since patch 6.2. And now that I think on it, I think its when I log out from the Island sanctuary instance specifically. There have been a few times were the inventory was saved and I believe this is when I was not logging out from the island.

Date & Time: since patch 6.2
Frequency: Regularly
World name: Adamantoise
Character name: Sorrel Ember
Party or solo: solo
In-game time: n/a
Area and coordinates: island sanctuary

I'm on PS5, not sure the specs are needed.