<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
Nothing fancy. Just copying recursively from a Linux server to a Windows drive.
After the error I was able to manually continue the download and it finished ok.

<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.7.6

Error message:
Invalid access to memory.

Stack trace:
(002F11E0)
(007E46BA)
(007E6722)
(007E369C)
(0005A7EA) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(0067FB56)
(0067F623)
(00717EBD)
(00715661)
(0071819C)
(00723685)
(00674527)
(00671727)
(0066FBD8)
(0008269F)
(00012388) kernel32.dll.BaseThreadInitThunk
(00038A00) ntdll.dll
(000389D0) ntdll.dll

(002F11E0)
(007E46BA)
(007E6722)
(007E369C)
(0005A7EA) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(0067FB56)
(0067F623)
(00717EBD)
(00715661)
(0071819C)
(00723685)
(00674527)
(00671727)
(0066FBD8)
(0008269F)
(00012388) kernel32.dll.BaseThreadInitThunk
(00038A00) ntdll.dll
(000389D0) ntdll.dll

(007E4D25)
(007E62FF)
(00715868)
(0071819C)
(00723685)
(00674527)
(00671727)
(0066FBD8)
(0008269F)
(00012388) kernel32.dll.BaseThreadInitThunk
(00038A00) ntdll.dll
(000389D0) ntdll.dll

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.