When a moving block and/or piston extends or retracts directly adjacent to redstone consumers, solid blocks connected to a redstone line, repeaters, and comparators, it causes lag if they are connected to fairly large amounts of redstone producers. 

Expected result: redstone components function fine with no excessive increase in lag

Actual result: redstone components function normally, however a noticable increase in lag also occurs

I had to crop the attached file a bit so it fit within the 10mb limit, although you can still see what happens