WinSCP 4.3.5 is over 6 years old. Please upgrade.

I invoke WinSCP 4.3.5 command interface(winscp.com) in a .NET/C# process running on Windows Server 2008 that connects to 3 different remote FTP sites to download files. This happens every 30 mins and the app runs 24/7. (An upgrade to 5.9.3 version is on the road map, although not immediately.)

All 3 run similar commands -
option batch on
open sftp://user:pass@site/ -timeout=120
synchronize local local_dir remote_dir -criteria=time

Sometimes, I see all 3 winscp sessions fail with an "Abnormal Program Termination" error message box. This happens rarely but when it happens, the impact is severe since the main process doesn't 'fail' and it requires user intervention to close the error messages.
I've handled the main process recovery, but I'm unclear as to why sporadically the winscp sessions fail and I can't recreate the error.

I've attached the Event Viewer details regarding the failure. I don't have the log files currently, but I've enabled logging now. I'm hoping there's some info in the attached log to identify the error.

Is this a known error, addressed in a newer version? If so, starting from which version was this solved?
Thanks much in advance.