Invalid access to memory - _ssh2_bpp_rekey_inadvisable

<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 5.17.6

Error message:
Invalid access to memory.

Stack trace:
(00BE9D1B) _ssh2_bpp_rekey_inadvisable
(00F87E4E) C5296_0
(00F89EB6) ____ExceptionHandler
(00F86C70) __ExceptionHandler
(00087E3F) ntdll.dll
(000732D1) ntdll.dll.KiUserExceptionDispatcher
(00BFF219) _ssh_ppl_user_output_string_and_free
(00BCDC46) C2603_0
(00BCDD39) _run_toplevel_callbacks
(00D077A8) TSecureShell::EventSelectLoop
(00D07E11) TSecureShell::Idle
(00D881FF) TTerminal::Idle
(000AF5C9) TTerminalManager::Idle
(00018C91) TCustomScpExplorerForm::Idle
(00049A73) TNonVisualDataModule::DoIdle
(00049A30) TNonVisualDataModule::SessionIdleTimerTimer
(003A4AC8) System::Classes::_18201
(000435C9) USER32.dll
(000240D7) USER32.dll
(00023229) USER32.dll
(0002300B) USER32.dll.DispatchMessageW

(00F884B9) C5296_0
(00F89A93) _ReThrowException
(000AF60E) TTerminalManager::Idle
(00018C91) TCustomScpExplorerForm::Idle
(00049A73) TNonVisualDataModule::DoIdle
(00049A30) TNonVisualDataModule::SessionIdleTimerTimer
(003A4AC8) System::Classes::_18201
(000435C9) USER32.dll
(000240D7) USER32.dll
(00023229) USER32.dll
(0002300B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.