maui upgrade from 2.1 to 17.3 - cannot reinstall plasma

[benit]

I still have the problem that I cannot "drag-and-position" a simple folder view widget. When I try to resize it a bit or re-position it a small amount, it completely jumps from right screen border to the left border. Very strange. I had the hope that this behaviour was a bug that had been solved in the new plasma version.

Could it make sense to re-create this widget now? Or is the widget "renewed" automatically with the new update?