Openlayers3- zoom in and drag the map, the building shows lag

[cscredhat]

I found two problems with OSMB-ol3.
1.When I zoom in and drag the map, the building shows lag.
2.Open the example in the small window, and then full screen browsing, the buildings still shows only the part that shows when the window is small， the other places of the browser don not show.
Is there any way to solve these two problems?