<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:
Cannot%20focus%20a%20disabled%20or%20invisible%20window%0D%0A%0D%0AStack%20trace%3A%0D%0A%28001DBBED%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3ASetFocus%0D%0A%280001048D%29%20TCustomScpExplorerForm%3A%3AExecuteFile%0D%0A%2800010B7E%29%20TCustomScpExplorerForm%3A%3AExecuteFile%0D%0A%2800016119%29%20TCustomScpExplorerForm%3A%3ADoDirViewExecFile%0D%0A%2800015FEE%29%20TCustomScpExplorerForm%3A%3ADirViewExecFile%0D%0A%28003D9E98%29%20Customdirview%3A%3ATCustomDirView%3A%3AExecute%0D%0A%280021C609%29%20Vcl%3A%3AControls%3A%3ATWinControl%3A%3AWndProc%0D%0A%2800260537%29%20Vcl%3A%3AComctrls%3A%3ATCustomListView%3A%3AWndProc%0D%0A%280034059C%29%20System%3A%3AClasses%3A%3A_18201%0D%0A%28000152F7%29%20USER32.dll%0D%0A%2800015D35%29%20USER32.dll%0D%0A%280001FD32%29%20USER32.dll%0D%0A%280001FD58%29%20USER32.dll.CallWindowProcW%0D%0A%28003FF173%29%20Dragdrop%3A%3ATDragDrop%3A%3AWndMethod%0D%0A%280034059C%29%20System%3A%3AClasses%3A%3A_18201%0D%0A%28000152F7%29%20USER32.dll%0D%0A%2800015D35%29%20USER32.dll%0D%0A%28000167CE%29%20USER32.dll%0D%0A%2800016895%29%20USER32.dll.DispatchMessageW

Status: not_matched

The problem happens rarely. I cannot reproduce it.