<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
I connected to a server via SFTP and started to download a 3.5 GB file. After a few minutes it crashed with the information submitted below.
I exited WinSCP, restarted it and restarted the download. This time it went through successfully.

BTW: Since the old DOS-days when IBM invented the "CUA"-menu, almost every program has in the upper left corner the menu "File New, File Open, File Exit". WinSCP in contrast has the command "Local" in this predominant position and hides "New" under "Commands" and "Exit" under "Session" in the middle of the menu bar. This may appear logical to someone who uses WinSCP every day, but to someone who uses different programs and got used to the CUA standard, it it appears quite puzzling.

<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.7.7

Error message:
Division by zero

Stack trace:
(006499DF)
(007E08AA)
(007E2912)
(007DF88C)
(0005A7EA) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(00078142)
(0070FE31)
(00649AB7)
(00649818)
(007160A1)
(00718CEC)
(007241D5)
(0001C75B)
(0003F31F)
(003E89CF)
(003E45A0)
(003D9992)
(003FF27F)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

(007E0F15)
(007E24EF)
(0064990C)
(00649818)
(007160A1)
(00718CEC)
(007241D5)
(0001C75B)
(0003F31F)
(003E89CF)
(003E45A0)
(003D9992)
(003FF27F)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

(007E0F15)
(007E24EF)
(007163B8)
(00718CEC)
(007241D5)
(0001C75B)
(0003F31F)
(003E89CF)
(003E45A0)
(003D9992)
(003FF27F)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.