I logged in today to find less inventory slots and some of my items nonexistent or not excess-able. Please help! Some of the items were from the winter event as well.  

Value pack expired?

Yea must been a expired Value pack, you just can get the items unlocked by writing ticket or buying new value pack..

god that they didnt fix this bug yet..  

Did the issue clear up ?

I think you need to sort your inventory. If the issue still persists  you must submit a ticket so customer service can help look into the issue. Here is the link for ticket submittal:

www.console.playblackdesert.com/support

Let me know how it goes!

CM Valtarra

You need to unsort inventory then drag items on locked slots manually (hold x then drag to open slot) that works for me