I had notice this same behavior from Firefox running Ubuntu Mate 17.04, with a slightly different discover.
One time I did notice the freeze, got a call and left the computer for a while, later to see that the Downloads folder did opened, but after several seconds.
Following that first long wait, the "Open Containing folder" works normally.
I had notice this same behavior from Firefox running Ubuntu Mate 17.04, with a slightly different discover.
One time I did notice the freeze, got a call and left the computer for a while, later to see that the Downloads folder did opened, but after several seconds.
Following that first long wait, the "Open Containing folder" works normally.