This happened for the very first time and it was also the very first error I ever had with WinSCP. I was uploading a .7z file of 37.5 GB. I'm still on Win7 Pro. Can be that the program 7zip still had a pointer onto this file. Nothing to worry about! Friendly greetings

WinSCP 6.1.2

Error message:
Unzulässiger Zugriff auf einen Speicherbereich.

Stapelverfolgung:
(000C12D5)
(0006246E) ntdll.dll
(0000F12E) ntdll.dll.KiUserExceptionDispatcher
(00024B84)
(00024E33)
(000BF6B7)
(00D21FD1)
(00D1E82D)
(0001BB4E)
(003CD663)
(0021564C)
(00015307) USER32.dll
(00015D45) USER32.dll
(000167D2) USER32.dll
(00016895) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.