This is caused by your windows are dropping below / rising above their home Storey while your Floor Plan Cut Plane is set to show 1 or more stories up / down. You can change your Floor Plan Cut Plane settings to no go outside your current storey, but this might not always be viable.
Alternatively, you could set the Floor Plan Display of your windows to Projected so that they only show when cut by your Floor Plan Cut Plane. Though this might cause other issues...
AC22-23 AUS 7000 Self-taught, bend it till it breaks. Win10 | E5620 x 2 | 24GB | K2200 RIP PSU Win10 | R5 2600 | 16GB | GTX1660