Launcher hangs at ‘finalising’ stage of loading - javaw.exe problem

Launcher hangs at ‘finalising’ stage of loading.
No error message displayed - just gets stuck as not responding.

Log file gives no clues, just goes from starting MC using javaw.exe to ‘NetQueue: Initiating shutdown. ... Game closed with id 1’

From other posts, have tried many things to fix it, including:

• run scannow & ccleaner
• point java executable to folder containing javaw.exe
• uninstall + reinstall MC (many times)
• completely removed old version of standalone java 8 (using java uninstall prog)
• removed any rogue entries in registry to old version of java
• removed Oracle symlink files
• added correct jre/bin folder to PATH environment variable
• tried clearing PATH environment variable
• added JAVA_HOME environment variable to pint to correct jre/bin folder
  but none of these fixed it.

After much digging, I found that trying to run javaw.exe from file explorer gave the message that Windows could not find the file (even though I had run it from the right folder). Verified that I got the same result by trying to run javaw.exe in a CMD window – same result, system cannot find file javaw.exe.

I then stumbled on a temporary workaround – accidentally ran java.exe instead of javaw.exe in the CMD window and this worked OK. So I tried pointing the java executable in Launcher and it worked.

My conclusion is that java.exe uses a slightly different routing to files/variables etc to javaw.exe, but I can’t work out where or how. Have tried looking for clues in the two versions of launcher_log.txt, but there’s too much of it and it’s beyond me!

Any clues or suggestions for how to get launcher to work correctly with javaw.exe?
Or, does anyone know how I can trace the routing of javaw.exe to see where it's ending up?