Grasshopper in rhino 6. Every second focus from grasshopper window changes to rhino window

I have found an interesting bug.
Rhino 6 - 90 trial version. The focus from the grasshopper window automaticaly changes to the rhino window every second ±.
During this changing every action made in grasshopper drops down or get unactiv. Menus, parameters and others are closing. Selected items are becomming unselect. It’s impossible to work with it.
For changing parameters or even for deleting nods you should do it in 1 sec. In other case the focus changes, menu closes and you should try it from the begining.
For example, I select some nods and trying to press “del” but nothing shanges because of automaticaly changing focus and the _delete comand apears in rhino comand line.
Have the same problem on two different comps. What could it be and how can i solve this problem?
Rhino 6 latest version, 90 trial, russian lang. grasshoper in complect without any other modules.