<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.7.7

Error message:
External exception C0000006

Stack trace:
(007DF82F)
(00062496) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(00769891)
(0076AFD5)
(0009F2DA)
(0009FA45)
(0009FC40)
(0000CC18)
(0000CFB0)
(0000D037)
(00031AE4)
(00382614)
(0016A155)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.