Backup database runs forever

I'm using pgAdmin 4.1 on Windows 10, PostgreSQL ver 9.6.1. 

I've started backup database process from the GUI. It was running for about 6 minutes than pgAdmin has unexpectedly stopped working. 

I've reopen pgAdmin. In the right bottom corner it is shown that backup is still running (http://prntscr.com/dcnxvm) . When I'm trying to connect to my databse via pgAdmin, pgAdmin crashes and stopes responding (http://prntscr.com/dcny1i). 

After reboot the problem is still here: 

Backup process shows as running in right bottom corner (272603.01 seconds running for now) and when I try to connect to my DB pgAdmin is stopping. Killing processes from task manager also have no effect. 

If needed I can provide additional information.

Will appreciate for any feedback.