I have had an issue with wasps making nests in the frames from 1998- to today. Called Pella. The girl said she had never heard of the problem before! I find that really hard to believe as I have been cleaning nests out every year when I clean the windows.
The whole spring along the top of the window is clogged with nests, I have to use a screwdriver and push the nest and bugs and dust out with someone hold the vacuum up there.
I would not buy Pella again!