In the last 10 days, WinSCP has now crashed for the third time with this error. The following describes the consistent circumstances that I believe (/am guessing) lead to this crash.
On Win 10 Pro, I'm running Firefox latest with about 6 windows open, and collectively hundreds and hundreds of tabs open. As Firefox runs this way, it continues to increase its use of system resources until the pc barely crawls.
To fight this Firefox problem, at night, I disable networking (via Control Panel > Network & Internet > Network Connections), and in the morning (after Firefox has all night to properly record/backup the current session), I use Resource Monitor to kill the primary Firefox task (almost always, the Firefox task with the most threads.) Once everything settles down, I restart Firefox (before reconnecting the network.) Then once Firefox has a chance to open all the tabs - and times them out because it can't connect - I re-enable the network. (This seems to keep Firefox better behaving for longer, as the tabs that never got reloaded don't seem to aggravate Firefox's drift to resource consumption.)
WHEN WinSCP crashes, it has been left on over night, with an active connection to another computer WHILE the Network has been Disabled. (When WinSCP is running, connected to an outside computer, and loses network connectivity, it constantly pops up a dialog box to say it has no connectivity, then counts down and retries the connection. This cycle goes on all night until the network connection restarts.) On the days when WinSCP hasn't crashed overnight, once the network is reconnected, it continues where it left off the night before with no problems - I don't restart it. (But since I've not seen WinSCP crash two days in a row, the crash may require the accumulations of 2 or 3+ nights of being shut off to cause the crash.)
I guessing that something in WinSCP's Alert/Retry loop for a failed network connection has some sort of (Probabilistic?) resource leak - perhaps exacerbated by the resource load Firefox presents (even with out network access, Firefox is constantly backing stuff up to disk.)
While the above does not produce a hard deterministic fail, 3 times in 10 days seems like a lead to investigate. As a guess, maybe there is a race condition that Firefox interferes with, causing the resource leak only sometimes. Then on nights where the there is enough accumulated leakage (perhaps from the Alert/Retry loop) WinSCP actually crashes.
I hope this helps. Contact me if you wish. Please start the email subject link with "WinSCP" as I get a lot of junk email, and generally visually scan the start of the subject line for keywords.)
Invalid access to memory.
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.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.