Hello PR9INICHEK.
It appears that there is no bug present.
(A) The vest is full - visible on the top bar
(B) Inventory storage is greyed out - Indicating inability to add more items.
(C) This can be little confusing - but we calculate both volume & weight. If one small but very heavy object is in a vest then vest is going to be full and you cannot carry more in it. Same goes if you have one light but large object in the vest, it also will be full and unable to contain any other items.