I filed a ticket and it hasn't been responded to in over 3 days, so I'm hoping someone else might see this.
I won 6 Twisted Vine Teas from the Morostide event. I wasn't sure if I was supposed to get those, so I filed a ticket and locked them. After locking them, I had 5. I was told I'm supposed to have them, and was asked if I had any other issues. I said that the quantity keeps changing, even when the item is locked and I haven't used any.
This happened with my Pet Ruby Widows, but the second I had all three again, I put them into my shop before the site could screw it up.
No other items in my inventory changed quantity like that.