VTK update 3D PointCloud too slow !

I use the VTK-7.1 and PCL 1.10 and Qt 5.12.8 to show 3D point cloud, it show’s normally the viewer can update everytimes. after I update VTK from 7.1 to 9.2.6, and PCL from 1.10 to 1.13 and Qt from 5 to 6, this problem happened. if you hold down the mouse button or keyboard, the viewer can show’s normally, if nothing is done, the display is very slow.
anyone can help me? thanks !