Hello,
Happened after disconnecting one of 3 tabs.
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.15

Error message:
Invalid access to memory.

Stack trace:
(007CDEAX) TTerminal::UpdateSource
(0006248E) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(007CE089) TTerminal::Source
(00815700) TLocationProfilesDialog::AddAsBookmark
(00818EFA) TLoginDialog::TLoginDialog
(00818C8D) DoLoginDialog
(0081AD70) TLoginDialog::UpdateControls
(0081A37A) TLoginDialog::LoadSession
(006CD9EF) TFTPFileSystem::HandleReplyStatus
(000189BD) TCustomScpExplorerForm::DoDirViewExecFile
(00048223) TScpExplorerForm::TScpExplorerForm
(000481E0) TScpExplorerForm::TScpExplorerForm
(003A346C) __tpdsc__ System::Masks::TMask::TMaskStates
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167BF) USER32.dll
(00016885) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.