This has been reported many times, most recently by Emma on 2019-08-27.
Sometimes when widgets are sized in a particular way on a particular screen size, the layout doesn't stay static but constantly switches between two options causing a constant flickering effect. Resizing the browser or widgets tends to fix this.
I've been able to recreate this by carefully resizing a browser window with a dashboard.
This has been reported many times, most recently by Emma on 2019-08-27.
Sometimes when widgets are sized in a particular way on a particular screen size, the layout doesn't stay static but constantly switches between two options causing a constant flickering effect. Resizing the browser or widgets tends to fix this.
I've been able to recreate this by carefully resizing a browser window with a dashboard.
Low priority.