Closing Kontakt 5 Hangs in Cubase

I can open up and use instruments within Kontakt 5, but whenever I close Kontakt, eg using the [x] in top right, then the Kontakt hangs, goes white. I can still hear audio but cannot do anything else. Its seems to close OK after maybe 1 minute wait.

Happens in 9.5 and also 10.

Windows 10, 64 bit, using the 64 bit version of Kontakt.

Any ideas?