UGENE hanged on cancelling assembly import

I've started import of the Klebsislla assemblies into a MySQL database in a local network. It takes time to import it. I didn't see the progress, so I must have imported it for several times.

That is why I started cancelling the importing tasks (3 or 4 tasks).

The last task was on about 33% and when I tried to delete it, UGENE hanged. I was not able to click anywhere in it or even close it.