Error reading MessageForm.Left: External exception C0000006

<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 5.21.2

Error message:
Error reading MessageForm.Left: External exception C0000006

Stapelverfolgung:
(003E8C52)

(003BB3E3)
(003BB61D)
(003BAE11)
(003BADC4)
(003C8A6D)
(0023C381)
(00E4D705)
(003B5C6A)
(003AB6AF)
(003AD003)
(003AD091)
(0023BB7A)
(00004CEE)
(00E4A4CA)
(00455370)
(00E50FD9)
(000F6E37)
(000F7740)
(000F78BE)
(000F79D4)
(0001125F)
(00011432)
(00011629)
(000117E7)
(000471BC)
(0040E060)

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.