Invalid access to memory

<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 6.1.1

Error message:
Invalid access to memory.

Stack trace:
(000BEE0B)
(000974CF) ntdll.dll
(00077751) ntdll.dll.KiUserExceptionDispatcher
(00D21711)
(00D1DF6D)
(0001BB4E)
(003CCDAF)
(00214D98)
(000312E1) USER32.dll
(00022001) USER32.dll
(000208C0) USER32.dll
(0002040B) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.