I am also facing the same problem, on registration, the cart gets emptied.
On top of this, there is another problem I am facing.
For example: let’s say when verified customers have some time saved in their cart (lets call it ‘cart 1’) and they logged out, next time when they visit the shop they add some items to the cart before login (let’s call this ‘cart 2’), after that when they log in the previously saved cart (cart 1) is destroyed and replaced with the current (cart 2).
This is not the same with the wish list though. Wishlist stays and updates with previous and current items.
I wonder if there is any fix so that the cart can work same as wishlist