I appreciate your helping
No, there is no problem in 4.16 regards this issue AFAIK - I am using TArrays
that retaining a lot of stuff and even sharing it with multiple threads…
As soon as specified as PROPERTY() all work at my end, for now I am using 4.16.3.
You have couple of things to do:
a) Debug your Code (if you can’t debug probably due to intensity of mouse events) LOG everything you can.
b) Review your Logic (all of it not just the item.h) - who creates/allocates it ? how is it done ? could it be Collected by GC at some stage ?
(Probably who ever retains “this” is the problem I have a feeling that your item itself is rapidly allocates and deallocates – “Rubber duck”[1] is the way to go if you work alone.
I think I can not help you more than this suggestion, since I don’t have your code (and I am also too lazy to debug it for you even if i had 
).
[1] Rubber Duck method: Rubber duck debugging - Wikipedia
Hmm English is such a… not logical language – LOG means a Wooden Log, and also a log as typing something to yourself – interesting why on earth it is the same word :-?
After checking with AddToRoot - it is unlikely.
I don’t know what is your C++ Level, but I would bet on a logical mistake.
Good Luck anyway!
well you have just ask the wrong person, I am not a native english speaker 
but I wish if I were, it would help alot.
not much if the scale of knowledge is ranked from 1 to 1000, I would say my level in c++ just 50 out of 1000 or might be less