<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 5.7.2

Error message:
Out%20of%20memory%0D%0A%0D%0AStack%20trace%3A%0D%0A%28003B17F2%29%20System%3A%3ANewUnicodeString%0D%0A%28003B17F2%29%20System%3A%3ANewUnicodeString%0D%0A%280033E71B%29%20System%3A%3AClasses%3A%3ATComponent%3A%3AUpdateAction%0D%0A%28001DB6EC%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3ACMActionUpdate%0D%0A%2800216E85%29%20Vcl%3A%3AControls%3A%3ATControl%3A%3AWndProc%0D%0A%280021B9C9%29%20Vcl%3A%3AControls%3A%3ATWinControl%3A%3AWndProc%0D%0A%28001D676C%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3AWndProc%0D%0A%280078A765%29%20Vclcommon%3A%3AC2516_0%0D%0A%2800216AC0%29%20Vcl%3A%3AControls%3A%3ATControl%3A%3APerform%0D%0A%28001E1923%29%20Vcl%3A%3AForms%3A%3ATApplication%3A%3ADispatchAction%0D%0A%280033F8EC%29%20System%3A%3AClasses%3A%3A_18201%0D%0A%28000152F7%29%20USER32.dll%0D%0A%2800015D35%29%20USER32.dll%0D%0A%2800015DE3%29%20USER32.dll%0D%0A%2800015E41%29%20USER32.dll%0D%0A%280000F117%29%20ntdll.dll.KiUserCallbackDispatcher%0D%0A%28000186C0%29%20USER32.dll.SendMessageW%0D%0A%2800211CCC%29%20Vcl%3A%3AControls%3A%3ASendAppMessage%0D%0A%28001DB3EA%29%20Vcl%3A%3AForms%3A%3A_16777%0D%0A%28001DB468%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3AUpdateActions

Status: not_matched

The problem happens rarely. I cannot reproduce it.