Refresh difference 32-bit vs 64-bit

My App uses a drop handler to allow multiple files to be dropped and processed onto its interface.
When I compile 32-bit, the listbox I add the dropped items to, refreshes in-between each dropped item keeping the user informed.
When I compile 64-bit, the listbox is only refreshed after the last dropped item is processed and all I see until then is a ‘beachball’
How can I force a refresh in the 64-bit compiled version and why does it behave differently?

And making the process run in a separate thread is not what I’m looking for, so I would prefer not to do that,
just like I did not have to in 32-bits.

Any suggestions?

I am not seeing any differences in de dropobject events.
That said, it is highly recommended to always collect all dropped files into an array and process the files outside the dropobject events.
Not doing this can lead into locking up your app (and other unwanted issues).

The beachball would indicate that too many things are carried out in an event.

And because of that you should be using threads. Even if you don’t want to.