Invalid access to memory

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WinSCP 5.13.1

Error message:
Invalid access to memory.

Stack trace:
(0000F06C)
(000689FA)ntdll.dll
(00068E5E)ntdll.dll
(0006B2C9)ntdll.dll
(0006B547)ntdll.dll

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.