What happens if you disable "Use double buffering" in the advanced options menu?
To get to the advanced options menu, make sure you're running the latest version of WA (3.6.31.0), then from the 4-tile WA main menu, click the bottom-right button with question marks, then click "Advanced".
Doing this might introduce screen tearing while scrolling, but might also fix frame drops. Please try this and tell me the results. I am not sure exactly what your problem is, so I'm not sure if it'll work, but I think it's useful to try.