Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.

<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
Uploaded since yesterday 2 files (around 8GB Size) clicked nothing pressed nothing. But upload continues.
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.5.1

Error message:
Invalid pointer operation