Strange behaviour of ESTK in Windows 10

The past two weeks I switched from W7 to W10 am still fixing strange things. Setting up W10 to what i expect from the system is tedious...

Now I'm testing ESTK. I have installed the latest version (Adobe ExtendScript Toolkit CC 4.0.0.1, ExtendScript 4.5.5 Script UI 6.2.2). In my FM-15 I have also installed my graphic library (script suite FMgraph.jsx).

Running one of the scripts developed in W7-time reveals a strange behaviour of ESTK:

Starting ESTK takes at last twice as long as on W7 (the very same machine!)

When I start the script with F5,

1. the diagram (drawing) is complete after 6 seconds, but ESTK is not ready at all for the next run,
2. this is indicataed by the hour glass appearing until second 21!
3. But beware, it takes another 10 seconds until I can really start the script again with F5
4. Leaving ESTK with the X button takes aeons and in most cases the app tilts!

See the video (it does not show step 3 and 4) https://daube.ch/zz_tests/W10-ESTK-strange.mp4 

BTW it is not possible in this darn forum to use this URL for "Insert Video". only this Youtube stuff is accepted.