Binary mode transfer problem

We have problem with binary mode transfer. It works OK for me, but not for my colleague. We have the same version (5.11.2) and I have not found any transfer related differences neither in settings nor in registry.
If my colleague transfers a file in binary mode, some bytes are replaced (f.e. from Unix to Windows each FD is replaced by AC, each FC by 87 etc.).
It seems that some codepage conversion takes a place, though I do not expect any conversion in binary mode.
Does anybody have an advice where can be the cause an how to fix it?

Please attach a full session log file both from your and colleague's machine (using the latest version of WinSCP).

First of all, sorry for delay. I had marked "notify me when a replay is posted", but I received no mail (maybe it fell into the spam).
Today another colleague find the same problem and also find the cause: the cause is not directly in WinSCP, but in the operating system. People who have the problem connect to Unix via another port and there is a modificated OpenSSH daemon bound to that port which contains among others also a character conversion. So sorry again - for disturbing.
Best regards, Martin