I use portable version of WinSCP 5.8.2 on Windows 10 32bit, everything is OK.
I tried to replace WinSCP.exe to latest portable one - 5.8.3 RC.
It started and works, but it does not read site bookmarks made by 5.8.2
When I returned 5.8.2 exe back - I see again my site bookmarks.
Seems a bug with 5.8.3 RC portable version, please, check.