My friend sent me 3 neutral capsules and asked me to pay her whatever price I want for them . I sent her money then open the capsule . I got 1 slime plant pot from one of them and after that my 2 other neutral capsule disapeard from my inventory.
Here is the trade log that I did receive 3 capsules and not only one. I only get 1 slime plant pot from the 3 capsule before 2 of them gone from my inventory. And no I didn't press delete items or anything. So right now seem like the system jsut eat my other 2 neutral capsules for no reason .

Well, since I was the one to send the trade, I'll try my best to answer this. If I remember correctly, I had all 3 neutral capsules put up in my usershop as 3 separate items. I recieved them at different days so they never were in my inventory simultaneously before. Once I removed them from my usershop, they stacked in my inventory, and the peculiar thing I noticed was that even though it was written "Neutral Capsule (x3)", only one of their IDs was displayed. I didn't pay it much mind and thought that the ID would change once the Capsule is opened, so I sent a personal trade with all of them stacked. Apparently it didn't go well.

@Komodo @Isegard
I investigated and for some reason the neutral capsule was defined as multiplication allowed. This should not happen anymore in the future, thanks for reporting!

@Isegard I sent you PC 28 as compensation.