Copying files to remote side failed - _ssh_hmac_sha1_96_buggy

<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 5.10

Error message:
Copying files to remote side failed.

Parent path not known

Stack trace:
(00899B75) _ssh_hmac_sha1_96_buggy
(0089B0A8) _in6addr_loopback
(007ABCC6) _SSL_alert_desc_string
(007ABF2D) _SSL_rstate_string
(007ACAB8) _SSL_CTX_use_RSAPrivateKey_file
(006E045C) TSFTPFileSystem::CustomReadFile
(006DF146) TSFTPFileSystem::ReadDirectory
(006DE17E) TSFTPFileSystem::ReadDirectory
(006DC528) TSFTPFileSystem::TryOpenDirectory
(000A0BC7) CopyParamListPopupClick
(00017742) KERNEL32.DLL.BaseThreadInitThunk
(0006487B) ntdll.dll.RtlGetAppContainerNamedObjectPath
(00064848) ntdll.dll.RtlGetAppContainerNamedObjectPath

I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.

Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.