[4.20] Hierarchical Instanced Static Mesh crash in many ways if used in C++

I’ve contacted support about my kind of this problem, and this is what I’ve got:

Actually the problem is when you are
calling AddInstance(). Every time you
call this function, a Build Tree is
called to run asynchronously. So when
you are copying and pasting your HISM,
it is creating 9 Build Trees to run
asynchronously at the same time, which
is highly inefficient. To circumvent
this you would set
HISMComponent->bAutoRebuildTreeOnInstanceChanges
to false before the loop then set it
back to true after the loop and call
HISMComponent->BuildTreeIfOutdated(true,
true);

This works, but not in all cases, so not sure is it will help you.
Try and reply please…