Furnace data deleted when entering portal and leaving nether for a certain amount of time

Steps to Reproduce:

1. Put some items in a furnace in the Nether Wastes
2. Leave the Nether
3. Wait in the overworld for a while
4. Come back to the Nether
5. Check the furnace

Expected Result :

The items are still there.

Observed Result :

The Items are gone.