I've sent you an email.

it is realtively easy to repro. We did some more testing by running only one sync at the same time. It still hangs once in a while. It is probably related to timeouts. The hang after timeout was probably not really fixed in 4.7. It still hangs after a timeout or after connecting again once a timeout occured before.
Jens

I do not see any obvious way how this can happen. Is it easy for you to reproduce the problem?

I'm using WinSCP to sync a directory to another host. The sync is in a script executed from the task scheduler.
I upgraded from 4.2.3 to 4.2.7 because of a hang condition that happend after a timeout. Now WinSCP hangs from time to time if it runs concurrently with other WinSCP clients. It appears the lock is on the stdio redirected log output. I'm redireting the output of winscp.com to a different log file for each instance that runs at the same time.
It must have something to do with how winscp.com receives the output from winscp.exe. With multiple instances running at the same time it appears to get confused and locks up. I saw log entires from the wrong instance in the wrong file just before it locks up.
Is that possible?
Jens