<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:
Out%20of%20memory%0D%0A%0D%0AStack%20trace%3A%0D%0A%28003B2452%29%20System%3A%3ANewUnicodeString%0D%0A%28003B2452%29%20System%3A%3ANewUnicodeString%0D%0A%280033F3CB%29%20System%3A%3AClasses%3A%3ATComponent%3A%3AUpdateAction%0D%0A%28001DC32C%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3ACMActionUpdate%0D%0A%2800217AC5%29%20Vcl%3A%3AControls%3A%3ATControl%3A%3AWndProc%0D%0A%280021C609%29%20Vcl%3A%3AControls%3A%3ATWinControl%3A%3AWndProc%0D%0A%28001D73AC%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3AWndProc%0D%0A%280078E0D1%29%20Vclcommon%3A%3AC2516_0%0D%0A%2800217700%29%20Vcl%3A%3AControls%3A%3ATControl%3A%3APerform%0D%0A%28001E2563%29%20Vcl%3A%3AForms%3A%3ATApplication%3A%3ADispatchAction%0D%0A%280034059C%29%20System%3A%3AClasses%3A%3A_18201%0D%0A%2800007E6F%29%20USER32.DLL.CallNextHookEx%0D%0A%28000080CC%29%20USER32.DLL%0D%0A%2800008327%29%20USER32.DLL%0D%0A%2800008527%29%20USER32.DLL%0D%0A%280003F594%29%20ntdll.dll.KiUserCallbackDispatcher%0D%0A%280000D8B4%29%20USER32.DLL.SendMessageW%0D%0A%280021290C%29%20Vcl%3A%3AControls%3A%3ASendAppMessage%0D%0A%28001DC02A%29%20Vcl%3A%3AForms%3A%3A_16777%0D%0A%28001DC0A8%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3AUpdateActions

Status: not_matched

The problem happens rarely. I cannot reproduce it.