I am using the latest Visual Studio as my editor. When WinSCP doesn't sense the change, I can usually wait a minute, resave the file, and it will get uploaded. Oftentimes I get frustrated and choose Stop, Start, and Yes in the "Keep remote directory up to date" dialog, and the file gets updated.
I see other posts about this, where you send a debug build, but I haven't seen a solution.
FWIW, it seems like this problem began about a month (or two) ago.