I was calculating the size of a folder when it stopped with this error. The size finished caluclating though and is accurate. I tried to reproduce the error but couldn't.

WinSCP 5.7.7

Error message:
External exception EEFFACE

Stack trace:
(000B2FC8) KERNELBASE.dll.RaiseException
(0007C53F) ntdll.dll
(00069D7A) ntdll.dll.KiUserExceptionDispatcher
(00496710)
(007E10FE)
(007E24EF)
(00013208)
(0077C578)
(0021801B)
(0021C609)
(00185074)
(0021C76F)
(0021C609)
(0021BC50)
(0034059C)
(00033921) USER32.dll
(0001378B) USER32.dll
(0001336B) USER32.dll
(0001A177) USER32.dll
(00069D54) ntdll.dll.KiUserCallbackDispatcher
(00012A2E) USER32.dll.SendMessageW
(0004FB87) COMCTL32.DLL
(0007DAD4) COMCTL32.DLL
(00033921) USER32.dll
(0001378B) USER32.dll
(00013522) USER32.dll.CallWindowProcW
(0021C71A)
(0021C609)
(00185074)
(0034059C)
(00033921) USER32.dll
(0001378B) USER32.dll
(0001308C) USER32.dll
(00012E4B) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.