<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 5.9.1

Error message:
メモリのアクセス違反

スタック トレース:
(00486B56) Pngfunctions::DrawPNG
(0008137F) ntdll.dll
(0006EF1A) ntdll.dll.KiUserExceptionDispatcher
(00489815) Pngimagelist::TPngImageList::DoDraw
(00199900) Vcl::Imglist::TCustomImageList::Draw
(001998B7) Vcl::Imglist::TCustomImageList::Draw
(004780AB) Tbxutils::DrawTBXIconShadow
(0046A338) Tbxofficexptheme::TTBXOfficeXPTheme::PaintImage
(0045BE5C) Tbx::TTBXItemViewer::DrawItemImage
(0045CDAB) Tbx::TTBXItemViewer::Paint
(0044FC47) Tb2item::TTBView::DrawItem

The problem happens rarely. I cannot reproduce it.